Random access procedures in wireless systems

ABSTRACT

A wireless transmit/receive unit (WTRU) may detect cell congestion by selecting a preamble type as a function of priority level, transmitting the preamble to a serving cell, receiving a random access response (RAR) from the serving cell, determining a congestion state of the serving cell as a function of the received RAR, and/or responding to the congestion state of the serving cell. RACH functionality may be improved by allocating one or more sets of Physical RACH (PRACH) resources to a WTRU. The WTRU may configure the additional PRACH resources based on the allocation. A WTRU may determine a second set of PRACH resources based at least in part on a first set of PRACH resources. A WTRU may determine additional sets of PRACH preambles and may utilize modified PRACH preambles and/or modified PRACH preamble formats. The WTRU may signal additional PRACH resources.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 61/611,836, filed Mar. 16, 2012; U.S. Provisional PatentApplication No. 61/644,562, filed May 9, 2012; and U.S. ProvisionalPatent Application No. 61/678,387, filed on Aug. 1, 2012; the contentsof which are hereby incorporated by reference herein.

FIELD

This disclosure is generally related to wireless communications.

BACKGROUND

Random Access Channel (RACH) resources may be utilized by wirelesstransmit/receive units (WTRUs) to perform uplink transmissions in eithera contention based or contention free manner. RACH procedures andresources may be used to request resources and/or to facilitate uplinktiming alignment.

SUMMARY

Methods and devices for indicating random access procedure priorityand/or detecting of cell congestion by a wireless transmit/receive unit(WTRU) are disclosed. Example methods may include selecting a preambletype as a function of priority level, transmitting the preamble to aserving cell, receiving a random access response (RAR) from the servingcell, determining a congestion state of the serving cell as a functionof the received RAR, and/or responding to the congestion state of theserving cell.

Systems and methods are disclosed for improving RACH functionality. Forexample, one or more sets of Physical RACH (PRACH) resources may beallocated to a WTRU. The WTRU may configure the additional PRACHresources based on the allocation. A WTRU may determine a second set ofPRACH resources, for example, based at least in part on a first set ofPRACH resources. The sets of PRACH resources may or may not overlap. AWTRU may determine additional sets of PRACH preambles and may utilizemodified PRACH preambles and/or modified PRACH preamble formats. Methodsfor signalling additional PRACH resources are disclosed. A WTRU may beconfigured to handle RACH failure on a second set of PRACH resources.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawingswherein:

FIG. 1A is a system diagram of an example communications system in whichone or more disclosed embodiments may be implemented;

FIG. 1B is a system diagram of an example wireless transmit/receive unit(WTRU) that may be used within the communications system illustrated inFIG. 1A;

FIG. 1C is a system diagram of an example radio access network and anexample core network that may be used within the communications systemillustrated in FIG. 1A;

FIG. 1D is a system diagram of an another example radio access networkand another example core network that may be used within thecommunications system illustrated in FIG. 1A;

FIG. 1E is a system diagram of an another example radio access networkand another example core network that may be used within thecommunications system illustrated in FIG. 1A;

FIG. 2 is a block diagram illustrating an example of E-UTRA RRC statesand mobility support between E-UTRAN, UTRAN, and GERAN;

FIG. 3 illustrates an example random access procedure that may beperformed;

FIG. 4 illustrates example time periods that may be associated with acyclic prefix and a data sequence for a random access preambletransmission;

FIG. 5 illustrates an example PRACH configuration information element(IE);

FIG. 6 illustrates an example PRACH configuration IE;

FIG. 7 illustrates an example configuration for distributing RACHpreambles;

FIG. 8 illustrates an example PRACH configuration IE;

FIG. 9 illustrates an example PRACH configuration IE;

FIG. 10 illustrates an example PRACH configuration IE;

FIG. 11 illustrates an example PRACH configuration IE;

FIG. 12 illustrates an example PRACH configuration IE;

FIG. 13 illustrates an example PRACH configuration IE;

FIG. 14 illustrates an example PRACH configuration IE;

FIG. 15 illustrates an example PRACH configuration IE; and

FIG. 16 illustrates an example PRACH configuration IE.

DETAILED DESCRIPTION

A detailed description of illustrative examples will now be describedwith reference to the various Figures. Although this descriptionprovides a detailed example of possible implementations, it should benoted that the details are intended to be exemplary and in no way limitthe scope of the application.

FIG. 1A is a diagram of an example communications system 100 in whichone or more disclosed embodiments may be implemented. The communicationssystem 100 may be a multiple access system that provides content, suchas voice, data, video, messaging, broadcast, etc., to multiple wirelessusers. The communications system 100 may enable multiple wireless usersto access such content through the sharing of system resources,including wireless bandwidth. For example, the communications systems100 may employ one or more channel access methods, such as code divisionmultiple access (CDMA), time division multiple access (TDMA), frequencydivision multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrierFDMA (SC-FDMA), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, and/or 102 d (whichgenerally or collectively may be referred to as WTRU 102), a radioaccess network (RAN) 103/104/105, a core network 106/107/109, a publicswitched telephone network (PSTN) 108, the Internet 110, and othernetworks 112, though it will be appreciated that the disclosedembodiments contemplate any number of WTRUs, base stations, networks,and/or network elements. Each of the WTRUs 102 a, 102 b, 102 c, 102 dmay be any type of device configured to operate and/or communicate in awireless environment. By way of example, the WTRUs 102 a, 102 b, 102 c,102 d may be configured to transmit and/or receive wireless signals andmay include user equipment (UE), a mobile station, a fixed or mobilesubscriber unit, a pager, a cellular telephone, a personal digitalassistant (PDA), a smartphone, a laptop, a netbook, a personal computer,a wireless sensor, consumer electronics, and the like.

The communications systems 100 may also include a base station 114 a anda base station 114 b. Each of the base stations 114 a, 114 b may be anytype of device configured to wirelessly interface with at least one ofthe WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to one or morecommunication networks, such as the core network 106/107/109, theInternet 110, and/or the networks 112. By way of example, the basestations 114 a, 114 b may be a base transceiver station (BTS), a Node-B,an eNode B, a Home Node B, a Home eNode B, a site controller, an accesspoint (AP), a wireless router, and the like. While the base stations 114a, 114 b are each depicted as a single element, it will be appreciatedthat the base stations 114 a, 114 b may include any number ofinterconnected base stations and/or network elements.

The base station 114 a may be part of the RAN 103/104/105, which mayalso include other base stations and/or network elements (not shown),such as a base station controller (BSC), a radio network controller(RNC), relay nodes, etc. The base station 114 a and/or the base station114 b may be configured to transmit and/or receive wireless signalswithin a particular geographic region, which may be referred to as acell (not shown). The cell may further be divided into cell sectors. Forexample, the cell associated with the base station 114 a may be dividedinto three sectors. Thus, in one embodiment, the base station 114 a mayinclude three transceivers, i.e., one for each sector of the cell. Inanother embodiment, the base station 114 a may employ multiple-inputmultiple output (MIMO) technology and, therefore, may utilize multipletransceivers for each sector of the cell.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 115/116/117,which may be any suitable wireless communication link (e.g., radiofrequency (RF), microwave, infrared (IR), ultraviolet (UV), visiblelight, etc.). The air interface 115/116/117 may be established using anysuitable radio access technology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 103/104/105 and the WTRUs 102a, 102 b, 102 c may implement a radio technology such as UniversalMobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA),which may establish the air interface 115/116/117 using wideband CDMA(WCDMA). WCDMA may include communication protocols such as High-SpeedPacket Access (HSPA) and/or Evolved HSPA (HSPA+). HSPA may includeHigh-Speed Downlink Packet Access (HSDPA) and/or High-Speed UplinkPacket Access (HSUPA).

In another embodiment, the base station 114 a and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Evolved UMTSTerrestrial Radio Access (E-UTRA), which may establish the air interface115/116/117 using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.16 (i.e.,Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000,CDMA2000 1×, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), InterimStandard 95 (IS-95), Interim Standard 856 (IS-856), Global System forMobile communications (GSM), Enhanced Data rates for GSM Evolution(EDGE), GSM EDGE (GERAN), and the like.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, and the like. In oneembodiment, the base station 114 b and the WTRUs 102 c, 102 d mayimplement a radio technology such as IEEE 802.11 to establish a wirelesslocal area network (WLAN). In another embodiment, the base station 114 band the WTRUs 102 c, 102 d may implement a radio technology such as IEEE802.15 to establish a wireless personal area network (WPAN). In yetanother embodiment, the base station 114 b and the WTRUs 102 c, 102 dmay utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, etc.) to establish a picocell or femtocell. As shown in FIG. 1A,the base station 114 b may have a direct connection to the Internet 110.Thus, the base station 114 b may not be required to access the Internet110 via the core network 106/107/109.

The RAN 103/104/105 may be in communication with the core network106/107/109, which may be any type of network configured to providevoice, data, applications, and/or voice over internet protocol (VoIP)services to one or more of the WTRUs 102 a, 102 b, 102 c, 102 d. Forexample, the core network 106/107/109 may provide call control, billingservices, mobile location-based services, pre-paid calling, Internetconnectivity, video distribution, etc., and/or perform high-levelsecurity functions, such as user authentication. Although not shown inFIG. 1A, it will be appreciated that the RAN 103/104/105 and/or the corenetwork 106/107/109 may be in direct or indirect communication withother RANs that employ the same RAT as the RAN 103/104/105 or adifferent RAT. For example, in addition to being connected to the RAN103/104/105, which may be utilizing an E-UTRA radio technology, the corenetwork 106/107/109 may also be in communication with another RAN (notshown) employing a GSM radio technology.

The core network 106/107/109 may also serve as a gateway for the WTRUs102 a, 102 b, 102 c, 102 d to access the PSTN 108, the Internet 110,and/or other networks 112. The PSTN 108 may include circuit-switchedtelephone networks that provide plain old telephone service (POTS). TheInternet 110 may include a global system of interconnected computernetworks and devices that use common communication protocols, such asthe transmission control protocol (TCP), user datagram protocol (UDP)and the internet protocol (IP) in the TCP/IP internet protocol suite.The networks 112 may include wired or wireless communications networksowned and/or operated by other service providers. For example, thenetworks 112 may include another core network connected to one or moreRANs, which may employ the same RAT as the RAN 103/104/105 or adifferent RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, i.e., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks. For example, the WTRU 102 c shown in FIG. 1A may be configured tocommunicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram of an example WTRU 102. As shown in FIG. 1B,the WTRU 102 may include a processor 118, a transceiver 120, atransmit/receive element 122, a speaker/microphone 124, a keypad 126, adisplay/touchpad 128, non-removable memory 130, removable memory 132, apower source 134, a global positioning system (GPS) chipset 136, andother peripherals 138. It will be appreciated that the WTRU 102 mayinclude any sub-combination of the foregoing elements while remainingconsistent with an embodiment. Also, embodiments contemplate that thebase stations 114 a and 114 b, and/or the nodes that base stations 114 aand 114 b may represent, such as but not limited to transceiver station(BTS), a Node-B, a site controller, an access point (AP), a home node-B,an evolved home node-B (eNodeB), a home evolved node-B (HeNB), a homeevolved node-B gateway, and proxy nodes, among others, may include someor all of the elements depicted in FIG. 1B and described herein.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 115/116/117. For example, in one embodiment,the transmit/receive element 122 may be an antenna configured totransmit and/or receive RF signals. In another embodiment, thetransmit/receive element 122 may be an emitter/detector configured totransmit and/or receive IR, UV, or visible light signals, for example.In yet another embodiment, the transmit/receive element 122 may beconfigured to transmit and receive both RF and light signals. It will beappreciated that the transmit/receive element 122 may be configured totransmit and/or receive any combination of wireless signals.

In addition, although the transmit/receive element 122 is depicted inFIG. 1B as a single element, the WTRU 102 may include any number oftransmit/receive elements 122. More specifically, the WTRU 102 mayemploy MIMO technology. Thus, in one embodiment, the WTRU 102 mayinclude two or more transmit/receive elements 122 (e.g., multipleantennas) for transmitting and receiving wireless signals over the airinterface 115/116/117.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as UTRA and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that may not be physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 115/116/117from a base station (e.g., base stations 114 a, 114 b) and/or determineits location based on the timing of the signals being received from twoor more nearby base stations. It will be appreciated that the WTRU 102may acquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, and the like.

FIG. 1C is a system diagram of the RAN 103 and the core network 106according to an embodiment. As noted above, the RAN 103 may employ aUTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102 cover the air interface 115. The RAN 103 may also be in communicationwith the core network 106. As shown in FIG. 1C, the RAN 103 may includeNode-Bs 140 a, 140 b, 140 c, which may each include one or moretransceivers for communicating with the WTRUs 102 a, 102 b, 102 c overthe air interface 115. The Node-Bs 140 a, 140 b, 140 c may each beassociated with a particular cell (not shown) within the RAN 103. TheRAN 103 may also include RNCs 142 a, 142 b. It will be appreciated thatthe RAN 103 may include any number of Node-Bs and RNCs while remainingconsistent with an embodiment.

As shown in FIG. 1C, the Node-Bs 140 a, 140 b may be in communicationwith the RNC 142 a. Additionally, the Node-B 140 c may be incommunication with the RNC 142 b. The Node-Bs 140 a, 140 b, 140 c maycommunicate with the respective RNCs 142 a, 142 b via an Iub interface.The RNCs 142 a, 142 b may be in communication with one another via anIur interface. Each of the RNCs 142 a, 142 b may be configured tocontrol the respective Node-Bs 140 a, 140 b, 140 c to which it isconnected. In addition, each of the RNCs 142 a, 142 b may be configuredto carry out or support other functionality, such as outer loop powercontrol, load control, admission control, packet scheduling, handovercontrol, macrodiversity, security functions, data encryption, and thelike.

The core network 106 shown in FIG. 1C may include a media gateway (MGW)144, a mobile switching center (MSC) 146, a serving GPRS support node(SGSN) 148, and/or a gateway GPRS support node (GGSN) 150. While each ofthe foregoing elements are depicted as part of the core network 106, itwill be appreciated that any one of these elements may be owned and/oroperated by an entity other than the core network operator.

The RNC 142 a in the RAN 103 may be connected to the MSC 146 in the corenetwork 106 via an IuCS interface. The MSC 146 may be connected to theMGW 144. The MSC 146 and the MGW 144 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices.

The RNC 142 a in the RAN 103 may also be connected to the SGSN 148 inthe core network 106 via an IuPS interface. The SGSN 148 may beconnected to the GGSN 150. The SGSN 148 and the GGSN 150 may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, suchas the Internet 110, to facilitate communications between and the WTRUs102 a, 102 b, 102 c and IP-enabled devices.

As noted above, the core network 106 may also be connected to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

FIG. 1D is a system diagram of the RAN 104 and the core network 107according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the air interface 116. The RAN 104 may also be in communicationwith the core network 107.

The RAN 104 may include eNode-Bs 160 a, 160 b, 160 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 160 a, 160 b, 160c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the eNode-Bs 160 a, 160 b, 160 c may implement MIMO technology. Thus,the eNode-B 160 a, for example, may use multiple antennas to transmitwireless signals to, and receive wireless signals from, the WTRU 102 a.

Each of the eNode-Bs 160 a, 160 b, 160 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the uplink and/or downlink, and the like. As shown in FIG. 1D, theeNode-Bs 160 a, 160 b, 160 c may communicate with one another over an X2interface.

The core network 107 shown in FIG. 1D may include a mobility managementgateway (MME) 162, a serving gateway 164, and a packet data network(PDN) gateway 166. While each of the foregoing elements are depicted aspart of the core network 107, it will be appreciated that any one ofthese elements may be owned and/or operated by an entity other than thecore network operator.

The MME 162 may be connected to each of the eNode-Bs 160 a, 160 b, 160 cin the RAN 104 via an S1 interface and may serve as a control node. Forexample, the MME 162 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 162 may also provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as GSM or WCDMA.

The serving gateway 164 may be connected to each of the eNode-Bs 160 a,160 b, 160 c in the RAN 104 via the S1 interface. The serving gateway164 may generally route and forward user data packets to/from the WTRUs102 a, 102 b, 102 c. The serving gateway 164 may also perform otherfunctions, such as anchoring user planes during inter-eNode B handovers,triggering paging when downlink data is available for the WTRUs 102 a,102 b, 102 c, managing and storing contexts of the WTRUs 102 a, 102 b,102 c, and the like.

The serving gateway 164 may also be connected to the PDN gateway 166,which may provide the WTRUs 102 a, 102 b, 102 c with access topacket-switched networks, such as the Internet 110, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and IP-enableddevices.

The core network 107 may facilitate communications with other networks.For example, the core network 107 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices. For example, the corenetwork 107 may include, or may communicate with, an IP gateway (e.g.,an IP multimedia subsystem (IMS) server) that serves as an interfacebetween the core network 107 and the PSTN 108. In addition, the corenetwork 107 may provide the WTRUs 102 a, 102 b, 102 c with access to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

FIG. 1E is a system diagram of the RAN 105 and the core network 109according to an embodiment. The RAN 105 may be an access service network(ASN) that employs IEEE 802.16 radio technology to communicate with theWTRUs 102 a, 102 b, 102 c over the air interface 117. As will be furtherdiscussed below, the communication links between the differentfunctional entities of the WTRUs 102 a, 102 b, 102 c, the RAN 105, andthe core network 109 may be defined as reference points.

As shown in FIG. 1E, the RAN 105 may include base stations 180 a, 180 b,180 c, and an ASN gateway 182, though it will be appreciated that theRAN 105 may include any number of base stations and ASN gateways whileremaining consistent with an embodiment. The base stations 180 a, 180 b,180 c may each be associated with a particular cell (not shown) in theRAN 105 and may each include one or more transceivers for communicatingwith the WTRUs 102 a, 102 b, 102 c over the air interface 117. In oneembodiment, the base stations 180 a, 180 b, 180 c may implement MIMOtechnology. Thus, the base station 180 a, for example, may use multipleantennas to transmit wireless signals to, and receive wireless signalsfrom, the WTRU 102 a. The base stations 180 a, 180 b, 180 c may alsoprovide mobility management functions, such as handoff triggering,tunnel establishment, radio resource management, traffic classification,quality of service (QoS) policy enforcement, and the like. The ASNgateway 182 may serve as a traffic aggregation point and may beresponsible for paging, caching of subscriber profiles, routing to thecore network 109, and the like.

The air interface 117 between the WTRUs 102 a, 102 b, 102 c and the RAN105 may be defined as an R1 reference point that implements the IEEE802.16 specification. In addition, each of the WTRUs 102 a, 102 b, 102 cmay establish a logical interface (not shown) with the core network 109.The logical interface between the WTRUs 102 a, 102 b, 102 c and the corenetwork 109 may be defined as an R2 reference point, which may be usedfor authentication, authorization, IP host configuration management,and/or mobility management.

The communication link between each of the base stations 180 a, 180 b,180 c may be defined as an R8 reference point that includes protocolsfor facilitating WTRU handovers and the transfer of data between basestations. The communication link between the base stations 180 a, 180 b,180 c and the ASN gateway 182 may be defined as an R6 reference point.The R6 reference point may include protocols for facilitating mobilitymanagement based on mobility events associated with each of the WTRUs102 a, 102 b, 102 c.

As shown in FIG. 1E, the RAN 105 may be connected to the core network109. The communication link between the RAN 105 and the core network 109may defined as an R3 reference point that includes protocols forfacilitating data transfer and mobility management capabilities, forexample. The core network 109 may include a mobile IP home agent(MIP-HA) 184, an authentication, authorization, accounting (AAA) server186, and a gateway 188. While each of the foregoing elements aredepicted as part of the core network 109, it will be appreciated thatany one of these elements may be owned and/or operated by an entityother than the core network operator.

The MIP-HA may be responsible for IP address management, and may enablethe WTRUs 102 a, 102 b, 102 c to roam between different ASNs and/ordifferent core networks. The MIP-HA 184 may provide the WTRUs 102 a, 102b, 102 c with access to packet-switched networks, such as the Internet110, to facilitate communications between the WTRUs 102 a, 102 b, 102 cand IP-enabled devices. The AAA server 186 may be responsible for userauthentication and for supporting user services. The gateway 188 mayfacilitate interworking with other networks. For example, the gateway188 may provide the WTRUs 102 a, 102 b, 102 c with access tocircuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. In addition, the gateway 188 mayprovide the WTRUs 102 a, 102 b, 102 c with access to the networks 112,which may include other wired or wireless networks that are owned and/oroperated by other service providers.

Although not shown in FIG. 1E, it will be appreciated that the RAN 105may be connected to other ASNs and the core network 109 may be connectedto other core networks. The communication link between the RAN 105 theother ASNs may be defined as an R4 reference point, which may includeprotocols for coordinating the mobility of the WTRUs 102 a, 102 b, 102 cbetween the RAN 105 and the other ASNs. The communication link betweenthe core network 109 and the other core networks may be defined as an R5reference, which may include protocols for facilitating interworkingbetween home core networks and visited core networks.

According to various disclosed examples, a WTRU may associate differentphysical random access channel (PRACH) resources and/or formats withdifferent random access channel (RACH) functions when triggering a RACHprocedure. For example, a WTRU may determine what PRACHresource/format/occasion to use for the transmission of a preamble in acell when multiple sets of PRACH resources may be configured. As anexample, a first PRACH configuration (e.g., first set of PRACHresources) may be used for a first set of functions (and/or a firsttraffic priority) and a second PRACH configuration (e.g., second set ofPRACH resources) may be used for a second set of functions (and/or asecond traffic priority). The first set of PRACH resources may be commonto the WTRUs within a cell and/or may be used for a random accessscheduling request that may be determined to be a high priority request.Examples of functions that may be associated with a high priorityrequest may include one or more of control plane signaling, VoIP orinteractive applications, an application with high QoS requirements,emergency call signaling, etc. The second set of PRACH resources may bespecific to a subset (e.g., one or more) WTRUs in a cell and/or may beused for a random access scheduling request that is determined to be alower priority request. Examples of functions that may be associatedwith a lower priority request may include one or more of best effortbackground traffic, highly delay tolerant packets, delay tolerantcontrol signaling, etc.

In an example, a mobile terminal (e.g., WTRU) may configure PRACHresources by performing one or more of multiplexing PRACH resources inthe time domain using a plurality of prach-ConfigIndex IE(s),multiplexing PRACH resources in the frequency domain using a pluralityof prach-FreqOffset Information Elements (IEs), and/or a combination oftime domain multiplexing and frequency domain multiplexing of PRACHresources. A WTRU may be configured to determine a second set of PRACHresources as a function of one or more of the PRACH configuration, theSFN, the start of the DRX on-duration, a semi-static PRACH Mask Index,the DRX On-Duration period, the DRX Active Time, the PRACH occasion usedfor initial preamble transmission, the configured density, and/or thelike. A WTRU may be configured to determine a corresponding set ofresources in case of resource overlap. A WTRU may be configured todetermine a second set of PRACH preambles, wherein the second set mayutilize a second rootSequenceIndex, the second set may utilize agrouping of preambles of a first set, and/or the second set may definemore (or less) than 64 preambles (e.g., longer T_(seq) or differentcoding). A WTRU may be configured to extend a preamble format withadditional uplink information. A WTRU may be configured to utilize PRACHresources with different preamble formats.

A WTRU may be configured to implement failure procedures for handlingRACH failure on a second set of PRACH resources. For example, the WTRUmay be configured to handle RACH failure on a second set of PRACHresources when uplink radio link failure (RLF) may not have occurred(e.g., the PRACH failure may be due to congestion handling). A WTRU maybe configured to revert to RACH on using a first PRACH configuration(e.g., using normal/legacy random access scheduling) based at on whetheror not UL RLF has occurred.

A WTRU may be configured to receive an indication regarding additionalPRACH resources. For example, a WTRU may receive one or more of aconfiguration with multiple PRACH-Config Information Elements (IEs) fora given cell, a configuration with multiple PRACH-ConfigInfo IEs for aPRACH-Config IE, a configuration with multiple prach-ConfigIndex IEs fora PRACH-ConfigInfo IE, a configuration with multiple prach-FreqOffsetIEs for a PRACH-ConfigInfo IE, a configuration with a newPRACH-ConfigDedicated-LowPrioSR IE that may include one or more of thepreviously listed configurations, and/or any combination thereof. Theconfigurations may be WTRU-specific (e.g., for WTRUs in a RRC_CONNECTEDmode) or may be cell-specific (e.g., for WTRUs in a RRC_IDLE mode).

3GPP LTE Release 8/9 may support up to 100 Mbps in the downlink (DL)and/or may support 50 Mbps in the uplink (UL) for a 2×2 MIMO (e.g.,Multiple Input-Multiple Output) antenna configuration. The LTE downlinktransmission scheme may be based on an orthogonal frequency divisionalmultiple access (OFDMA) air interface. For the purpose of flexibledeployment, LTE R8/9 systems may support scalable transmissionbandwidths. For example, a WTRU may be configured to support one or moreof 1.4, 2.5, 5, 10, 15 or 20 MHz.

For example, each radio frame (e.g., 10 ms) may include 10 equally sizedsubframes, each with a duration of 1 ms. Each subframe may include twoequally sized timeslots with a 0.5 ms duration. There may be 6 or 7orthogonal frequency division multiplexing (OFDM) symbols per timeslot.For example, seven OFDM symbols may be used for timeslot including anormal cyclic prefix length, and six OFDM symbols per timeslot may beused in a system configuration that utilizes an extended cyclic prefix.The subcarrier spacing for the LTE R8/9 system may be 15 kHz. A reducedsubcarrier spacing mode using 7.5 kHz is may also be utilized.

A resource element (RE) may correspond to a single subcarrier during asingle OFDM symbol interval. Twelve consecutive subcarriers during a 0.5ms timeslot may correspond to one resource block (RB). Therefore, withseven OFDM symbols per timeslot, each RB may include 12*7=84 REs. A DLcarrier may include a scalable number of resource blocks, for example,ranging from six RBs to 110 RBs. A range of 6-110 RBs may correspond toan overall scalable transmission bandwidth of roughly 1 MHz up to 20MHz. In an example, a set of common transmission bandwidths may bespecified, for example over 1.4, 3, 5, 10 or 20 MHz.

In an example, the basic time-domain unit that may be used for dynamicscheduling may be one subframe that may include two consecutivetimeslots. Resource blocks corresponding to the same frequency domainresources in the two slots of the subframe may be referred to as aresource-block pair. Certain subcarriers on some OFDM symbols may beallocated to carry pilot signals in the time-frequency grid. In anexample, a certain number of subcarriers at the edges of thetransmission bandwidth may be refrained from being utilized fortransmission in order to comply with spectral mask configurations. LTEmay support Frequency Division Duplex (hereinafter FDD or framestructure 1) and/or Time Division Duplex (hereinafter TDD or framestructure 2).

LTE-Advanced with Carrier Aggregation (e.g., LTE R10+) is an evolutionthat aims to improve data rates of single carrier LTE R8/9/10+ using,among other methods, bandwidth extensions also referred to as CarrierAggregation (CA). With CA, a WTRU may transmit and/or receivesimultaneously over the Physical Uplink Shared Channel (PUSCH) and/orthe Physical Downlink Shared Channel (PDSCH) of multiple Secondaryserving Cells (SCells). For example, one or more SCells may be utilizedfor transmission and/or reception in addition to a Primary serving Cell(PCell). For example, carrier aggregation of 4 SCells with the PCell maysupport flexible bandwidth assignments up to 100 MHz.

The control information for the scheduling of PDSCH and PUSCH may besent on one or more Physical Downlink Control Channel(s) (PDCCH(s)). Forexample, in addition to the “straight” scheduling using one PDCCH for apair of UL and DL carriers in a given cell, cross-carrier scheduling mayalso be supported for a given PDCCH. Cross-carrier scheduling may allowthe network to provide PDSCH assignments and/or PUSCH grants in one cellfor transmissions/receptions in other serving cell(s).

Radio Resource Control (RRC) may handle the control plane signaling andthe exchange of layer 3 messages between an enhanced Node B (eNB) andthe WTRU. For LTE R8/9/10+, an Evolved Universal Terrestrial RadioAccess (E-UTRA) may define a number of RRC states (e.g., two RRCstates): RRC_CONNECTED and RRC_IDLE. The WTRU may be in theRRC_CONNECTED state when an RRC Connection has been established. If anRRC Connection has not been established, the WTRU may be in the RRC_IDLEstate.

In the RRC_IDLE state, the WTRU may monitor the paging channel to detectincoming calls, change of system information, and possibly also EarlyTerrestrial Warning System (ETWS)/Commercial Mobile Alert System (CMAS)notifications. The WTRU may also perform neighboring cell measurementsand cell selection or reselection and system information acquisition.

In the RRC_CONNECTED state, the WTRU may transmit or receive on unicastchannels and may monitor the paging channel and/or System InformationBlock (SIB) Type 1 to detect incoming calls, change of systeminformation, and possibly also ETWS/CMAS notifications. The WTRU mayalso be configured with one or more secondary cells in addition to theprimary cell.

In addition to the above states, a number of transition conditions,messages (e.g., Protocol Data Units (PDUs)), and procedures may bedefined. FIG. 2 illustrates an example of E-UTRA RRC states, including aRRC_IDLE state 202 and a RRC_CONNECTED state 204, and mobility supportbetween E-UTRAN, UTRAN, and GERAN.

A control channel, for example, a Physical Downlink Control Channel(PDCCH) may be used by the network (e.g., by an eNB) to assign resourcesfor downlink transmissions on a PDSCH and to grant resources for uplinktransmissions on a PUSCH to the WTRU.

The WTRU may request radio resources for an uplink transmission, forexample, by transmitting a scheduling request (SR) to the eNB. The SRmay be transmitted either on dedicated resources (D-SR) on a PhysicalUplink Control Channel (PUCCH), if configured, or using the RandomAccess procedure, for example, Random Access Channel (RACH) or RA-SR.

The WTRU may be granted radio resources by the eNB for a transmission onPUSCH, indicated in a grant that may be received on the PDCCH inconfigured resources, for example, a Semi-Persistently Scheduled ULgrant and/or a dynamically scheduled UL grant. In a given uplinktransmission, a WTRU may include a Buffer Status Report (BSR) indicatingthe amount of data in a buffer of the WTRU. The trigger to transmit aBSR may trigger a scheduling request.

For Frequency Division Duplex (FDD), considering the processing delaysin the WTRU (3 ms) and in the eNB (3 ms), and considering thetransmission interval for each subframe in the uplink (1 ms) and for thedownlink (1 ms), the Round-Trip Time (RTT) may be fixed, for example, at8 ms. For Time Division Duplex (TDD), given the varying uplink anddownlink subframe allocation, the RTT may be a function of saidallocation.

The WTRU may determine whether or not it may act on control signaling ina given subframe by monitoring the PDCCH for specific data controlinformation (DCI) messages (DCI formats) scrambled using a known radionetwork temporary identifier (RNTI) in specific locations, or searchspace, using different combinations of physical resources, for example,control channel elements (CCEs), based on aggregation levels, eachcorresponding, for example, to 1, 2, 4, or 8 CCEs used to transmit theDCI. A CCE may consist of 36 QPSK symbols, or 72 channel coded bits.

The PDCCH may be conceptually separated in two distinct regions. The setof CCE locations in which a WTRU may find DCIs it may act on may bereferred to as a Search Space (SS). The SS may be conceptually splitinto the common SS (CSS) and WTRU-specific SS (WTRUSS). The CSS may becommon to all WTRUs monitoring a given PDCCH, while the WTRUSS maydiffer from one WTRU to another. Both SS may overlap for a given WTRU ina given subframe, as this may be a function of the randomizationfunction, and this overlap may differ from one subframe to another.

The set of CCE locations that make up the CSS, and its starting point,may be a function of the cell identity and the subframe number. For LTER8/9, for example, DCIs may be transmitted with AL4 (4 CCEs) or AL8 (8CCEs) in the CSS. For a subframe for which the WTRU monitors the PDCCH,the WTRU may attempt to decode two DCI format sizes, for example,formats 1A and 1C and format 3A used for power control, in up to fourdifferent sets of four CCEs for AL4 (e.g., 8 blind decoding) and up totwo different sets of eight CCEs for AL8 (e.g., 4 blind decoding) for atotal of twelve blind decoding attempts in the CSS.

The CSS may correspond to CCEs 0-15, implying four decoding candidatesfor AL4 (e.g., CCEs 0-3, 4-7, 8-11, and 12-15), and two decodingcandidates for AL8 (e.g., CCEs 0-7 and 8-15).

The set of CCE locations that makes up the WTRUSS, and its startingpoint, may be a function of the WTRU identity and the subframe number.For LTE R8/9, DCIs may be transmitted with AL1, AL2, AL4, or AL8 in theWTRUSS. For a subframe, for which the WTRU monitors the PDCCH, the WTRUmay attempt to decode two DCI formats in up to six different CCEs forAL1 (e.g., 12 blind decoding), up to six different sets of two CCEs forAL2 (e.g., 12 blind decoding), up to two different sets of eight CCEsfor AL8 (e.g., 4 blind decoding), and up to two different sets of eightCCEs for AL8 (e.g., 8 blind decoding), for a total of 32 blind decodingattempts in the WTRUSS.

Depending on the connection of the WTRU to the network, capabilities,and supported features, the WTRU may monitor one or more RNTIs forgrants, assignments, and other control information from the eNB. Forexample, a System Information RNTI (SI-RNTI) may be cell-specific, andmay be used to indicate scheduling of system information on PDSCH, forexample in the CSS. A Paging RNTI (P-RNTI) may be assigned to multipleWTRUs for decoding of the paging notification, for example, in RRC_IDLEmode, in the CSS.

A Random Access RNTI (RA-RNTI) may be used to indicate scheduling of theRandom Access Response (RAR) on PDCCH, and may unambiguously identifywhich time-frequency resource was used by a WTRU to transmit the randomaccess preamble. The WTRU may find corresponding DCI on PDCCH using theRA-RNTI, and may then receive the RAR on PDSCH. The RA-RNTI may beassociated with/correspond to a Physical Random Access Channel (PRACH)of the PCell in which the Random Access Preamble was transmitted, andmay be determined as:RA-RNTI=1+t_id+10*f_id  (1)where t_id may be the index of the first subframe of the specified PRACH(0≦t_id<10), and f_id may be the index of the specified PRACH withinthat subframe, in ascending order of frequency domain (e.g., 0≦f_id<6).Thus, theoretically for a subframe there may be 10 transmissionopportunities for a given PRACH in the time domain and 6 transmissionopportunities in the frequency domain for the given PRACH, so there maybe a total of 60 different PRACH transmission opportunities in thetime-frequency grid for a given PRACH (e.g., per SFN). However, in mostpractical deployments the actual number of opportunities in a givensubframe may be lower due to the actual PRACH configuration, collisionswith other signaling, and other transmission issues.

A Multimedia Broadcast and Multicast Services (MBMS) RNTI (M-RNTI) maybe cell-specific and may be used to decode the notification of a changeon the MBMS control channel (MCCH) in the CSS. A Cell RNTI (C-RNTI) maybe a WTRU-specific RNTI and may be used to decode PDCCH forcontention-free grants and assignments, for example, for DCIs in theWTRUSS. A Temporary C-RNTI may be used to decode the MSG4 message forthe contention-based procedure, and/or before the WTRU gets assigned itsown C-RNTI.

A Semi-Persistent Scheduling C-RNTI (SPS-C-RNTI) may be used to activatea semi-persistent downlink allocation on PDSCH or uplink grant on thePUSCH, in the WTRUSS. There may also be other RNTIs, including, forexample, transmit power control (TPC)-PUSCH-RNTI and TPC-PUCCH-RNTI,which may be used for power control of the PUSCH and PUCCH,respectively.

For LTE R8/9/10+, multiple control information messages, for example,DCIs, may be received by a given WTRU on PDCCH in each subframe. Forexample, multiple DCIs may be received for a WTRU configured with asingle serving cell. There may be one UL grant and one DL assignmentwith C-RNTI/SPS-C-RNTI. The UL grant and/or the DL assignment may beabsent. There may be one message with P-RNTI (paging) and one messagewith SI-RNTI (SI change notification) in the CSS. The message withP-RNTI and/or the message with SI-RNTI in the CSS may also be absent.

The WTRU may initiate the RA procedure when any of a number of eventsoccurs. For example, the WTRU may initiate the RA procedure when theWTRU attempts to obtain initial access to the network to establish anRRC connection. As another example, the WTRU may initiate the RAprocedure when the WTRU accesses the target cell during a handoverprocedure. As another example, the WTRU may initiate the RA procedurewhen the WTRU is perform an RRC Connection Re-establishment procedure.As another example, the WTRU may initiate the RA procedure when the WTRUis be instructed by the network to perform the RA procedure, forexample, by a PDCCH RA order (e.g., for DL data arrival). The WTRU mayinitiate the RA procedure when the WTRU determines that it has data totransmit. For example, the WTRU may determine to send a schedulingrequest, but may lack dedicated resources on PUCCH for sending therequest. For example, the WTRU may have new UL data to transmit that maybe of a higher priority than existing data in its buffer (e.g., and/orwas previously indicated in a previous BSR) and may send a SR to thenetwork via the RACH. When a WTRU already has data in its buffer, ascheduling request may be triggered if new data that arrives is of ahigher priority than existing data. If there is no data in the WTRU'sbuffer, any data that arrives in the buffer may trigger the SR. A SR maybe triggered by a BSR. A SR may indicate that the WTRU needs resources,while a BSR may indicate how much the WTRU has in its buffer.

Depending on whether or not the WTRU is assigned dedicated RACHresources, for example, a specific preamble and/or PRACH resources, theRA procedure may either be contention-free (CFRA) or contention-based(CBRA). FIG. 3 illustrates an example RA procedure 300 (e.g., a RACHprocedure) that may be performed. A MSG0 message may be applicable tonetwork-initiated RACH procedures. A MSG0 message may be received by theWTRU at 302 and may include DCI received on the PDCCH indicating that aRACH should be performed. The RACH procedure may include a MSG1 message.At 304, a preamble transmission (MSG1) on a resource of the PhysicalRandom Access Channel (PRACH) may be transmitted. The RACH procedure mayinclude a MSG2 message, which may include a Random Access Response (RAR)message. At 306, a MSG2 message may be received from an eNB and maycontain a grant for an uplink transmission and a Timing Advance Command(TAC).

Additionally, for CBRA, at 308, a MSG3 message may be transmitted fromthe WTRU, for example to facilitate contention resolution. The MSG3message may contain a BSR, signaling data, and/or user plane data. TheRACH procedure may include a MSG4 message that may be applicable toCBRA. The MSG4 message may be applicable to contention resolution.Contention resolution may be performed at 310. For example, the WTRU maydetermine whether or not it successfully completed the RACH procedurebased on either C-RNTI on PDCCH or WTRU Contention Resolution Identityon DL-SCH. The MSG4 message may be received by the WTRU.

In 3GPP LTE R8, R9, R10, and Release 11 (R11), there may be a singlePRACH configured for a given cell. For example, there may be a singleset of PRACH resources in a cell. For FDD (frame structure 1), a WTRUmay be configured by a higher layer configuration, for example fromreception of broadcast System Information or from reception of dedicatedsignaling, possibly with at most one PRACH resource for any givensubframe that is configured with available PRACH resources.

For TDD (frame structure 2), due to the nature of the UL/DL subframeconfiguration, frequency multiplexing may additionally be used when timemultiplexing may not be sufficient to obtain the desired PRACH density.In an example, the WTRU may be configured by a higher layerconfiguration, for example, from reception of broadcast SystemInformation or from reception of dedicated signaling, with one or morePRACH resources for each subframe configured with available PRACHresources. Each PRACH may be associated with an offset(prach-FrequencyOffset) that may indicate the first Physical ResourceBlock (PRB) of the PRACH in that subframe, for example, the first PRB ofthe six PRBs used for the preamble. Each PRACH may be indexed (f_id)based on increasing frequency domain indices. When frequencymultiplexing may be used, there may be multiples of six PRBs for PRACHavailability in the given subframe. Each set of six PRBs may represent asingle PRACH opportunity.

When the WTRU may perform the random access procedure, the WTRU maytransmit a preamble on an uplink resource of a configured PRACH, if aPRACH resource is available in the given subframe. Each random accesspreamble may occupy a bandwidth corresponding to six consecutiveresource blocks, for example, for both the FDD and the TDD framestructures. A WTRU may be configured with multiple groups of preambles(e.g., group A, group B, etc.) for the random access procedure on agiven serving cell. The selection of the preamble group may be afunction of the size of the MSG3 message. For example, selection of thepreamble group may be based on whether the data to transmit is largerthan a threshold size indicated for group A. In an example, selection ofthe preamble group may be a function of the radio conditions in thecell. For example, the selection of the preamble group may be based onthe estimated DL pathloss to ensure that the DL pathloss does not exceeda given value.

According to an example, FIG. 4 illustrates example time periods thatmay be associated with a cyclic prefix 402 and a data sequence 404 for arandom access preamble transmission. The physical layer random accesspreamble may include a cyclic prefix of length T_(cp) and a sequencepart of length T_(seq) (e.g., 0.8 ms). T_(cp) may be approximately 0.1ms, 0.68 ms, and/or 0.2 ms, depending on the preamble format used. Therespective lengths for T_(cp) and/or T_(seq) may depend on the framestructure (e.g., FDD(1) or TDD(2)) and/or the random accessconfiguration. For example, the respective lengths for T_(cp) and/orT_(seq) may depend on whether a FDD(1) or a TDD(2) frame structure isused. Preamble formats (e.g., formats 0, 1, 2, 3, and/or 4) may bedefined. The length of each of the preamble formats for T_(cp) andT_(seq) may depend on the preamble format used. For example, preambleformat 4 may be applicable to frame structure 2 (TDD).

For preamble format 2 (e.g., 2 ms) and 3 (e.g., 3 ms), the sequence,which may have a length of 0.8 ms, may be repeated twice. There may be amaximum of 64 different preambles in a given cell, which may correspondto six bits transmitted as the Sequence T_(seq) in the preamble formatof FIG. 4. The WTRU may determine whether or not preamble group B isavailable based on the parameters numberOfRA-Preambles andsizeOfRA-PreamblesGroupA. If these parameters differ, then there may betwo preamble groups (e.g., A and B). For example, in LTE R10, thePRACH-Config IE may specify the PRACH configuration. For example, thePRACH configuration IE may include a information element 500 as shown,for example, in FIG. 5.

The WTRU may use the parameter rootSequenceIndex to determine the 64preamble sequences for a given cell. The PRACH-ConfInfo IE may beincluded in the PRACH-Config IE and may indicate the root sequence. Forexample, the PRACH-ConfigInfo IE may include a information element 600as shown, for example, in FIG. 6. The parameter prach-ConfigIndex mayindicate which of the 64 possible configurations for the specific framestructure (e.g., FDD or TDD) may be used to determine the set of PRACHresources available in the cell. The WTRU may use this information todetermine the PRACH Resource Indexing for the cell. The parameterprach-FreqOffset may indicate the first PRB of the PRACH in a givensubframe. For example, the parameter prach-FreqOffset may indicate thefirst PRB of the six PRBs used for preamble transmission. For framestructure 2 (TDD) and preamble format 4, frequency multiplexing may beperformed according to a function of the number of DL to UL switchingpoint.

The transmission of a random access preamble may be limited to certaintime and frequency resources. These resources may be enumerated inincreasing order of the subframe number (e.g., subframe number 0, 1, 2,. . . , 9) within a radio frame (e.g., 10 ms) and the PRBs in thefrequency domain, such that PRACH Resource index 0 may correspond to thelowest numbered PRB and subframe within that radio frame. When the WTRUmay be assigned a dedicated resource, the WTRU may perform thetransmission of the preamble on the PRACH resource that may correspondto the indicated ra-PRACH-MaskIndex (e.g., index 0, 1, 2, . . . , 15)according to a mapping between the indicated value and the allowed PRACHresource(s) for that value. For example, a “0” may correspond to allresources, a 1 may correspond to index 0, 11 may correspond to the firstresource in an even PRACH opportunity in the time domain, etc.

For LTE R10, a WTRU may have a single set of PRACH resources (given byprach-ConfigIndex), where each resource may be indexed using a PRACHResource Index (e.g., referenced using ra-PRACH-MaskIndex) for a given10 ms radio frame. The PRACH resource with the lowest index in a givensubframe with PRACH may be indicated by prach-FreqOffset.

For FDD (frame structure 1), there may be one resource per subframe andthe indexing range may be from 0 to 9, inclusive. For TDD (e.g., framestructure 2), frequency multiplexing may be possible, where the numberof PRACH resources per subframe with PRACH may be a function of theprach-FreqOffset, the density value, the frequency resource index (Fra)for the given density, the system frame number (e.g., forpreamble/format 4), and/or the number of DL to UL switch points withinthe radio frame.

The WTRU may be configured, using RRC, with dedicated resources for thetransmission of a channel quality indication (CQI), precoding matrixindicator (PMI), and/or rank indication (RI) reports and/or forscheduling requests (D-SR). In addition, a WTRU may be configured withdedicated uplink resources for SPS. For example, the WTRU may beconfigured with a PUSCH resource for UL SPS, as well as with an uplinkPUCCH resource for HARQ A/N for a corresponding DL SPS configuration.The network may also assign a WTRU with dedicated SRS resources toassist scheduling decisions in allocation of uplink resources for PUSCHtransmissions.

For a WTRU configured with a single serving cell, PUCCH Type 2 resourcessuch as used for CQI/PMI/RI reports, may be explicitly assigned to theWTRU by the network using RRC signaling. For example, PUCCH Type 2resources may be contained in a distinct set of explicitly administeredresources. In an example, for LTE R8/9/10+DL SPS transmissions, fourPUCCH indices for PUCCH Type 1 HARQ A/N may be explicitly signaled tothe WTRU using RRC signaling.

The WTRU may additionally be configured with a semi-static resourceallocation on PUCCH for transmission of PUCCH format 3, and/or with aplurality of resources for transmission of PUCCH format 1b with channelselection.

A discrete Fourier transform spread (DFTS)-OFDM based LTE uplinktransmission may allow for uplink intra-cell orthogonality, which mayimply that uplink transmissions received by the eNB from differentmobile terminals may not interfere with each other. To maintain thisorthogonality, transmissions from different mobile terminals within thesame subframe but within different frequency resources may arrive at theeNB approximately time-aligned, where the margin of error may be withinthe cyclic prefix length. The cyclic prefix may be a guard interval inthe time domain that may be added to each symbol to handle channel delayspreading. For LTE, the generic frame structure with normal cyclicprefix length may contain seven symbols, and the cyclic prefix lengthmay be 5.2 μs for the first symbol and 4.7 μs for other symbols of theframe. For larger cells, an extended prefix may also be configured.

The timing advance may be a negative offset, at the WTRU, between thestart of a received downlink subframe and a transmitted uplink subframe.For example, the subframe for the uplink transmission may start ahead ofthe downlink subframe at the WTRU. The offset may be adjusted by thenetwork using, for example, TA Command (TAC) signaling. For example,adjustments may be based on previous uplink transmissions by the WTRU,including Sounding Reference Signals (SRS) and/or any other uplinktransmissions.

Before a WTRU may perform uplink transmissions for periodic SRS or anuplink transmission on PUCCH (e.g., HARQ A/N feedback, SR, periodicCQI/PMI/RI reports) or PUSCH, the WTRU may determine a proper timingalignment with the network. Uplink synchronization may be initiallyachieved using the RACH procedure, and the network may subsequentlytransmit TA Commands (TAC) in the downlink to maintain proper timingalignment. When the WTRU may receive the TAC, the WTRU may restart theTime Alignment Timer (TAT). In an example, the TAT may have values ofsf500, sf750, sf1920, sf2560, sf5120, sf10240, and/or infinity. A TACmay be received in the RAR during the RA procedure or in a TimingAdvance MAC Control Element.

When the TAT is running, the WTRU may transmit on a PUCCH resource in asubframe for which the WTRU may not perform a PUSCH transmission (e.g.,single carrier property). PUCCH resources may be dynamically allocatedfor HARQ A/N feedback for a PDSCH transmission in a frequency/timeshared resource of the PUCCH region. The WTRU may determine which PUCCHresource to use based on, for example, the first CCE of the DCI receivedon PDCCH that indicated the PDSCH assignment.

The TAT may expire for a synchronized WTRU, for example, when the WTRUmay not receive a TA Command (TAC) from the network for at least aperiod equal to the configured value of the TAT. For example, the TATmay range from 500 ms to 10240 ms, if enabled. A WTRU may not receive aTAC if each of the transmitted TACs may be lost during that period, forexample, following the consecutive loss of multiple TACs. This may be arare error case that may be reduced or minimized by a schedulerimplementation that may use sufficient repetitions. In an example, aWTRU may not receive a TAC if the network does not transmit one (e.g.,for the purpose of implicitly releasing dedicated uplink resources whenthe network may no longer schedule the WTRU for new transmissions).Accordingly, the validity of the timing advance for the WTRU may beimplicitly determined by the WTRU based on control signaling sent or notsent by the eNB.

When the TAT expires, the WTRU may release dedicated uplink resources.For example, any configured SRS resources and/or PUCCH resources forD-SR, CQI/PMI/RI or any configured downlink and uplink SPS resources maybe released. For example, when the TAT expires, the WTRU may release anyconfigured downlink and uplink SPS resources.

Additionally, the WTRU may determine not to perform any PUCCH or PUSCHtransmissions once it may not be considered synchronized with thenetwork. One motivation to avoid uplink transmission from WTRUs that mayno longer be synchronized may be to avoid possible interference to thetransmission of other WTRUs. In addition, stopping uplink transmissionupon lack of synchronization may provide implicit means for the WTRU todetermine that the scheduler may have revoked dedicated uplinkresources, for example, by making such a determination upon the TATexpiring following the absence of TACs from the network.

Signaling Radio Bearers (SRBs) may be radio bearers that may be used forthe transmission of RRC and NAS messages. For example, SRB0 may be usedfor RRC messages using the Common Control Channel (CCCH) logicalchannel. SRB1 may be used for RRC messages, possibly with a piggybackedNAS message, and/or for NAS messages prior to establishment of SRB2using the Dedicated Control Channel (DCCH) logical channel. SRB2 may beused for NAS messages and may be configured after activation ofsecurity. Once security may be activated, RRC messages on SRB1 and SRB2may be integrity protected and ciphered. Data Radio Bearers (DRBs) maybe radio bearers that are used for the transmission of user plane data(e.g., Internet Protocol (IP) packets).

A service that may generate user plane data may be associated with aRadio Access Bearer (RAB). A WTRU may be configured with one or moreRABs, and different RABs may terminate in a different packet datanetwork (PDN) gateway PGW in the core network (CN). A RAB may beassociated with a DRB. A RAB may be associated with a specific set ofQuality of Service (QoS) characteristics. The network may configure aDRB according to a desired level of QoS. For example, the network mayconfigure a DRB with parameters such as logical channel (LCH) priority,Prioritized Bit Rate (PBR), and/or PDCP SDU discard timer, according tothe desired level of QoS.

A DRB may be associated with a default EPS bearer and/or to a dedicatedbearer. Applications may use bearers (e.g., default and/or dedicated)according to the given QoS supported by those bearers. Packet filtersmay be used in the WTRU, for example, for uplink data, and in the CN,for example, for downlink data, to determine how to associate an IPpacket with a given bearer.

A service may generate user plane data that may involve different QoSlevels. For example, a Voice over IP (VoIP) application may generate areal-time transport protocol (RTP) voice/audio stream using a given UDPport and exchange RTP control (RTCP) protocol packets using a differentUDP port. In this example, the RTP flow may use a first RAB, while theRTCP flow may use a second RAB. The WTRU may be configured to determine,for each generated IP packet, which RAB the packet should be transmittedon. For example, the WTRU may use packet filters and/or Traffic FlowTemplates (TFTs) to make the determination. The WTRU may be configuredwith packet filters or TFTs by the network.

One or more EPS bearer(s) may be setup or removed for a WTRU given usinghigher layer procedures. The WTRU may maintain any default EPS bearer(s)and any other associated dedicated bearer(s) in the context of the WTRUas long as the WTRU may be attached to the network. For example, EPSbearers may be maintained in the context of the WTRU independently ofthe state of the RRC connection, for example, even when in idle mode.EPS bearers may be removed when the WTRU performs the detach procedurefrom UTRA. EPS bearers may be removed when the WTRU performs a detachprocedure from E-UTRA/UTRA. When the WTRU releases an RRC connection,any radio access bearers (e.g., SRBs and/or DRBs) may also be released.For example, the S1u connection and associated context between the eNBand SGW may be released.

WTRUs and other wireless devices may support a wide variety ofapplications, often in parallel. One or more of the applications mayhave different traffic characteristics and requirements. Many suchapplications may be agnostic to the technology used for the transmissionof their data, and/or may be ill-suited for wireless transmissions. Forexample, in case an application may generate small amounts of datatraffic with relatively long periods of low volume at intermittentintervals, a WTRU may be idle for long periods while it may stillregularly have to connect to the network to exchange small amounts ofdata.

A WTRU may be configured in a variety of manners. Tradeoffs may beachieved between data transfer latency, power consumption, controlsignaling overhead, and/or network efficiency. For example, a WTRU maybe in the RRC_CONNECTED state for a very long period of time for thebenefit of low control signaling overhead and low data transfer latency.However, remaining in this state for a long time may be at the expenseof battery usage and/or network resource efficiency when dedicatedresources may remain committed but not fully utilized. In an example, aWTRU may periodically transition between the RRC_CONNECTED and RRC_IDLEstates for the benefit of low power consumption. However, such a schememay result in increased data transfer latency and/or additional controlsignaling overhead.

In an example where one or more applications may remain constantlyactive (and/or semi-constantly active), and may generate backgroundtraffic at regular and/or irregular intervals, the aggregated sum from aplurality of WTRUs operating in such a manner may lead to increasedcommitment of PUCCH resources for dedicated scheduling requests (D-SR).Such resources may remain underutilized and may lead to increasedsignaling in order for the WTRU to be kept with proper uplink timingalignment. Moreover, utilizing the RA-SR often to request resources maycause network-related impairments, such as increased load on the PRACH,where random access procedures initiated by different WTRUs and/or fordifferent purposes may compete with each other, thereby increasing theprobability of preamble collisions, delays, and/or unsuccessfulcompletion. For example, RA-SR triggered for transmission of lowerpriority background traffic may contend with RACH for other purposesthat may be of a higher priority (e.g., connection establishmentprocedures for initial access or recovery procedures, connections foremergency access).

The methods described herein may address how to indicate priorityinformation while accessing the network and/or requesting uplinkresources; how to receive an indication of, and/or how to determinewhether there is congestion in the radio network; and/or how to respondto congestion in the radio network. The methods disclosed herein mayalso include: methods to configure additional PRACH resources; methodsto determine a second set of PRACH resources within configured resourcesets; methods to determine the set of PRACH resources to be used forpreamble transmission in case of overlap between a first and a secondset of configured PRACH resources; methods to determine a second set ofPRACH preambles; methods to extend preamble format for a given set ofPRACH resources; methods to handle sets of PRACH resources of differentphysical resource length; methods to handle RACH failure on a second setof PRACH resources; and/or the like.

Also disclosed herein are systems and methods based on RA-SR that mayavoid the inefficient allocation of PUCCH resources, as well as to avoidthe periodic generation of uplink transmissions to maintainsynchronization for a WTRU, for example when the WTRU may be in someform of “dormant” state with background data to transmit intermittently.Such systems and methods may minimize the impact of RA-SR procedure andcorresponding preamble (re)transmission(s) to the RACH procedure ofother WTRUs in the same cell. For example prioritization on RACH may beutilized to ensure that certain procedures that may be considered ofhigher priority (e.g., for RA-SR for higher priority data, forconnection establishment, for mobility, for emergency calls, and/or forrecovery purposes) are not unduly delayed or prevented. Such savings maybe achieved by methods that minimize the risk of preamble collisions inthe shared PRACH resources in a given cell.

When referred to herein, the term Multiple PRACH UE (MPUE) and/or theterm multiple PRACH WTRU (MPWTRU) may refer to WTRUs that may supportand/or operate according to a configuration with a plurality of PRACHresource sets/configurations and related methods.

When referred to herein, the term Single PRACH UE (SPUE) and/or the termSingle PRACH WTRU (SPWTRU) may refer to legacy WTRUs that lack supportfor the methods described with respect to a configuration with aplurality of PRACH resource sets/configurations. The terms SPUE and/orSPWTRU may also refer to MPUEs/MPWTRUs that may support such methods butare not currently operating according to the use of multiple PRACHresources.

When referred to herein, the term PRACH resource may refer to the firstPRB (e.g., frequency) of a set of consecutive PRBs that may be used forthe transmission of a preamble and/or to the set of consecutive PRBsthat may be used for the transmission of a preamble (e.g., typically 6PRBs).

When referred to herein, the term PRACH opportunity may refer to a PRACHresource in a given subframe (e.g., in time).

When referred to herein, the term PRACH occasion may refer to a subframe(e.g., in time) in which there may be one or more available PRACHopportunities.

When referred to herein, the term first set of PRACH resources may beassociated with a PRACH configuration that may be cell-specific. Forexample, the first set of PRACH resources may refer to a set of PRACHresources associated with a configuration received on the broadcastchannel in the system information. The first set of PRACH resources maygenerally refer to PRACH resources that may be used by SPUEs. The firstset of PRACH resources may generally refer to a default configurationfor performing random access in a given cell.

When referred to herein, the term second set of PRACH resources may beassociated with a PRACH configuration that may be configured for WTRUsthat implement one or more of the methods described herein for operatingwith an additional set of PRACH resources in addition to the first setof PRACH resources. The second set of PRACH resources may refer to PRACHresources that are implemented in addition to the PRACH resources thatmay be utilized by SPUEs.

In an example, a priority level may be associated with a configurationused to perform a transmission. For example, a WTRU may be configured todetermine which of a plurality of configurations to use when performingan uplink transmission. The first configuration may be associated with afirst priority level and a second configuration may be associated with asecond priority level. For example, the priority level may be based on acharacteristic and/or a priority of the data to be transmitted and/orbased on a state of the WTRU (e.g., a dormant state as a substate of theRRC_CONNECTED state).

In an example, a priority level may be associated with data to betransmitted and/or an event generating the data. For example, a WTRU mayassociate a priority level with data that has become available fortransmission, with an event that triggered the transmission of suchdata, to an event that generated such data, and/or with a trigger for arandom access procedure.

For example, a WTRU may implement implementation-specific and/orproprietary methods such that user data generated by, for example, abest-effort non-critical background application may be associated with alower priority level than data from other applications, such as thosetransmitting real-time interactive (e.g., voice), best-effortinteractive (e.g., web browsing) data, emergency call data, and/orcontrol plane signaling. As another example, such priority level may bedetermined from the event that generated the data to the transmitted.For example, control plane signaling may generally be considered asbeing of a higher priority level than user plane data. However, suchcontrol signaling may be generated and available for transmission as theresult of user plane data of lower priority being generated by anapplication and being available for transmission. In such a case, thecontrol signaling may be considered to be of a priority that isequivalent to that of the corresponding user plane data. For example, aNAS Connection Establishment Request initiated for the purpose ofestablishing a best-effort default bearer for the transmission of datathat is determined to correspond to best-effort, intermittent backgroundtraffic, or identified as such, may be associated with a lower prioritylevel (e.g., the lowest priority level).

As another example, while not precluding other methods, a WTRU mayimplement methods such as those described in U.S. patent applicationSer. No. 13/436,457, filed Mar. 30, 2012, which is incorporated byreference herein in its entirety. Such methods may include theimplementation of a dormant behavior and/or state and/or implementationof a specific radio bearer, for example, an XRB, for the transfer ofdata from background applications. The methods described herein may beapplicable for a WTRU that is in a RRC_CONNECTED state or in a RRC_IDLEstate and/or a WTRU that uses a dormant behavior.

In an example, a priority may be associated with the random accessprocedure and/or to different aspects of a RACH procedure. For example,a priority may be associated with a PRACH configuration, a PRACHresource index, a preamble group, a preamble, and/or the like. While notlimited to such association, such priority may correspond with thepriority of the data and/or of the event that triggered the randomaccess procedure.

Priority may be a function of one or more factors, for example invarious combinations. For example, priority may be a function of aroaming state or a roaming agreement. A roaming WTRU may consider thatit does not have to enforce priorities and may treat all of its bearers'requests with equal priority (e.g., high priority). Priority may be afunction of the activation of a service or application. For example, aWTRU may support a service that is activated with a given priority(e.g., for a free service), the priority may be set to a low priority,while otherwise (e.g., for a paid service), the priority may be set to ahigh priority.

Priority may also be a function of whether the service was initiated bythe WTRU or by the network. For example, if the application or serviceis initiated by the network, corresponding data and/or requests may betreated with a higher priority for the duration of the application orservice.

As another example, priority may be a function of a prioritizationmechanism (e.g., Access Class Barring, Service-Specific Access Control,Extended Class Barring, etc.). For example, if the WTRU determines thata prioritization mechanism is activated for the cell, it may enforcepriorities according to the corresponding policies, while otherwise(e.g., if a prioritization mechanism is not activated for the cell) theWTRU may not enforce priorities.

Priority may also be a function of whether or not an application wasalready ongoing when the prioritization mechanism was activated. Forexample, while a prioritization mechanism is activated, the WTRU maydetermine that prioritization may be applied according to configuredpolicies for applications or services that were not ongoing when themechanism was activated. In an example, such applications or servicesmay be associated with a low priority upon activation of aprioritization mechanism.

Priority may also be a function of WTRU capabilities, such as supportfor a specific feature and/or application class. For example, a WTRU mayenforce policies if it has previously signaled that the feature issupported, while such signaling may be optional when the WTRU is in aroaming state. For example, one such feature may be Access Control for aspecific device class, for a specific application, and/or for a specificservice class. One such application, which may be prioritized, mayinclude packet-based services, such as Disaster Message Board serviceand/or a Disaster Voice Messaging service.

As another example, priority may be a function of an RRC state (e.g.,whether the WTRU is in an IDLE mode, a CONNECTED mode, or in a modecorresponding to a dormancy mode). For example, the WTRU may enforcepolicies related to prioritization while the WTRU is in a state that isdifferent than RRC_IDLE mode.

Prioritization may be preconfigured or received as a configurationaspect by the WTRU with a list of prioritized applications, for example,according to operators' policies.

While the general principles, methods, and related examples disclosedherein may be described in the context of 3GPP LTE technology andrelated specifications, such systems and methods may be equallyapplicable to any wireless technology implementing methods for a dormantmode of operation and/or methods for battery savings in general, such asother 3GPP technology based on Wideband Code Division Multiple Access(WCDMA), High Speed Packet Access (HSPA), High-Speed Uplink PacketAccess (HSUPA), and High-Speed Downlink Packet Access (HSDPA). In anexample, the methods described herein may be used while the WTRU isoperating according to a dormant behavior, but not when the WTRU isfully connected and/or in IDLE mode.

In an example, a WTRU may be configured to perform a WTRU-autonomousRACH procedure. The methods described herein, while not limited to, maybe applicable to a random access procedure that may be triggeredautonomously by the WTRU. For example, the WTRU may apply any of themethods described herein according to any of the following triggers forthe RACH procedure: connection establishment, mobility event, recoveryevent, scheduling Request (RA-SR), and/or when data becomes availablefor transmission in the buffer(s) of the WTRU. In an example, themethods described herein may be applicable to a network-initiated RACHprocedure and/or to a WTRU initiated RACH procedure, although theexamples described herein may describe that the network initiated RACHprocedures utilize the first set of PRACH resources.

The methods described herein may be used while the WTRU is operatingaccording to a dormant behavior. The WTRU may receive the configurationdescribed herein from dedicated signaling or from the broadcast systeminformation, or by a combination of both.

The WTRU may indicate priority information when performing a preambletransmission (MSG1) during a random access procedure. The WTRU mayperform preamble type selection, preamble selection, preamble groupselection, PRACH selection, PRACH opportunity selection, PRACH lengthselection, dynamic scheduling of a PRACH occasion, and/or indication inthe SR.

For preamble type selection (e.g., determining whether to use a randompreamble or a dedicated preamble), the WTRU may select a preamble typeas a function of the priority level associated with the procedure. Forexample, the WTRU may be configured with one or more dedicatedpreamble(s), where one or more, possibly each, may be associated with agiven priority level. For example, the WTRU may be configured with adedicated preamble that may be used for a procedure initiated with afirst priority and/or for a first function. The WTRU may also beconfigured with another dedicated preamble that may be used for aprocedure initiated with a second priority and/or a second function.

For preamble group selection (e.g., determining whether to use anexisting preamble group or a new preamble group), the WTRU may select apreamble group as a function of the priority level associated with theprocedure. For example, the WTRU may be configured with one or moregroup(s) of preambles. One or more preamble groups (e.g., each preamblegroup), may be associated with a given priority level. For example, theWTRU may be configured with a preamble group C that includes a number ofpreambles, dedicated or not. The WTRU may select a preamble from thispreamble group C for a procedure initiated with a first priority level.

For PRACH selection, for example selection of a set of PRBs within asubframe to be used for preamble transmission (e.g., f_id, where0≦f_id≦6), the WTRU may select a PRACH resource as a function of thepriority level associated with the procedure. For example, the WTRU maybe configured with one or more PRACHs, where at least one (e.g., eachPRACH) may be associated with a given priority level. The WTRU may beconfigured with multiple PRACHs in the same subframe. For example, for agiven subframe, the WTRU may be configured with a first PRACH that maybe used for a procedure initiated with a first priority and with asecond PRACH that may be used for a procedure initiated with a secondpriority. For example, a PRACH may refer to a specific set of PRACHresources, such a specific set of frequency resources that may beutilized for a PRACH transmission at a PRACH occasion.

For PRACH opportunity, for example, timing based on PRACH and a subframewithin a frame (e.g., t_id) the WTRU may select a PRACH opportunity as afunction of the priority level associated with the procedure. Forexample, the WTRU may be configured with one or more PRACH opportunitiesfor a given PRACH, where one or more PRACH opportunities may beassociated with a given priority level. For example, for a given PRACH,the WTRU may be configured with a first PRACH opportunity or a first setof PRACH opportunities that may be used for a procedure initiated with afirst priority. The WTRU may also be configured with a second PRACHopportunity or a second set of PRACH opportunities that may be used fora procedure initiated with a second priority.

For PRACH length, for example, the number of PRBs used for the preambletransmission, the WTRU may select a preamble length as a function of thepriority level associated with the procedure. For example, the WTRU maybe configured such that a given PRACH may support transmission of apreamble on a different number of PRBs. The WTRU may then be configuredsuch that a preamble transmission using a first set of PRBs (e.g., afirst number of PRBs) may be associated with a first priority, while apreamble transmission using a second set of PRBs (e.g., a second numberof PRBs) may be associated with a second priority. When the WTRU mayinitiate a random access procedure of a first priority, the WTRU maytransmit the preamble on the selected first set of PRBs. When the WTRUmay initiate a random access procedure of a second priority, the WTRUmay transmit the preamble on the selected second set of PRBs.

The WTRU may be configured with a specific RNTI, for example,PRACH-RNTI, or PR-RNTI, for dynamic scheduling of PRACH resources. TheWTRU may be configured with some or all of the above parameters with aPRACH configuration. The PRACH configuration may be associated with, forexample, the PR-RNTI. The WTRU may receive the PR-RNTI and/or the PRACHconfiguration from the broadcast system information, or by dedicatedsignaling (e.g., RRC messages). The WTRU may use the PR-RNTI to decodeone or more DCI in a given subframe. Such a subframe may be anysubframe, for example, a continuous PR-RNTI decoding during a giveninterval, a subset of subframes within a frame, for example, indicatedin a PRACH configuration such as using a bitmask, or recurringperiodically, for example, for subframes that match SFN mod(X)=0, whereX may be indicated in a PRACH configuration.

The DCI may include one or more of a carrier indicator, an index to aPRACH configuration, a resource block assignment, a frequency offset forPRACH, a preamble format, a SFN, and/or timing information. The carrierindicator may be, for example 0 or 3 bits. The resource block assignmentmay be the first PRB of the PRACH resource. The SFN may be codedinformation (e.g., Even, Odd, Any, etc.). The timing information mayindicate in what subframe the corresponding preamble transmission shouldbe performed (e.g., a value x). The DCI may also include padding bits.

In an example, the DCI may include an index to a PRACH configuration andpadding bits. The WTRU may use the indicated PRACH configuration for thepreamble transmission. In another example, the DCI may include aresource block assignment, timing information, and/or padding bits. TheWTRU may determine what PRACH resource to use starting from theindicated PRB and subsequent PRBs (e.g., the following five PRBs when aPRACH resource may be six PRBs) available for the transmission of apreamble in subframe n+x, where n is the subframe of DCI reception. Inanother example, the DCI may consist of padding bits. The WTRU may usethe configured PRACH information for the preamble transmission.

The PR-RNTI and/or the PRACH configuration may be available for RA-SRfor certain types of traffic, such as high priority traffic, lowpriority traffic, and/or EDDA (e.g., enhancement for diverse dataapplications) traffic EDDA traffic may include intermittent transfers ofsmall amounts of data, such as traffic generated by applications runningin the background. The corresponding PRACH resources may be availablewhen they are scheduled by the PR-RNTI. Successful decoding of thePR-RNTI may indicate that the corresponding PRACH resource may beavailable to the WTRU for PRACH transmission.

For example, the WTRU may start decoding the PDCCH for PR-RNTI when theWTRU determines that it may perform an SR. In particular, the WTRU mayperform an SR where the SR may be triggered for data of a priorityassociated with the PRACH configuration, for example, from dataassociated with EDDA traffic. If the PR-RNTI may be common for WTRUs ina given serving cell, the WTRU may decode DCIs in the common searchspace of the PDCCH. The WTRU may have received the corresponding PRACHconfiguration on a broadcast channel, for example, for WTRUs in an IDLEmode. In an example, if the PR-RNTI may be dedicated to a given WTRU orto a group of WTRUs in a given serving cell, the WTRU may decode DCIs inthe common search space and/or in the WTRU dedicated search space of thePDCCH. The WTRU may have received the corresponding PRACH configurationby dedicated signaling, for example, for WTRUs in a CONNECTED mode, orfor WTRUs in an IDLE mode if the configuration may be persistent until afirst mobility event. For example, a first mobility event may be a cellreselection or handover event.

If the WTRU successfully decodes a DCI on the PDCCH with the PR-RNTI, itmay initiate the transmission of a preamble in the corresponding PRACHresource (e.g., the resource indicated in the DCI). The correspondingpreamble transmission may be performed at subframe n+x, where n is asubframe of DCI reception and x is a processing delay. For example, theprocessing delay may be equal to six subframes. The DCI for PR-RNTI mayinclude timing information, for example, the value of x, and/orfrequency information for the PRACH resource, as described above.

In an example, preamble retransmission(s) may be performed on anexplicitly scheduled PRACH resource, for example, using PR-RNTI asdescribed above.

If used in combination with preamble group selection, the WTRU mayperform the selection of a preamble according to a preamble groupingthat may be specific to this procedure. For example, the WTRU may selecta group of preambles as a function of the size of data and/or the DLpathloss, such that it may further help the network to determine thesize of a grant for the first transmission following the successfulRA-SR.

In an example, if the WTRU reaches a threshold number (e.g., a maximumnumber) of preamble transmissions using the resources indicated in thegrant coded with the PR-RNTI, the WTRU may cancel the corresponding SRfor congestion control. This threshold number may be configured by thenetwork. The WTRU may initiate a normal scheduling request (e.g., alegacy RACH SR procedure), for example if this method is used to manageuplink resources. For example, the WTRU may initiate a normal SR byusing PRACH resources according to known procedures, such as LTE R8procedures.

For indication in the SR, the WTRU may indicate the priority of the datausing a two-bit SR message, for example, similar to PUCCH format 1a or1b. The indication may be in a PUCCH region separate from the single-bitSR region. The SR may convey a single-bit message indicating that theWTRU may have new data to transmit. The second bit in the SR message mayindicate the priority of the data that the WTRU may have to transmit.For example, if the value of the second bit is 0, it may indicate thatthe WTRU may have low priority data to be transmitted. If the value ofthe second bit is 1, it may indicate that the WTRU may have highpriority data to transmit in its buffer. It will be appreciated that avalue of the second bit of 0 may indicate high priority, while a valueof the second bit of 1 may indicate low priority. The network may handlethe scheduling request based on the indication from the WTRU. When theWTRU may transmit a two-bit scheduling request, the network mayimplicitly assume that the SR is for EDDA-type data because the WTRU maynot transmit a two-bit SR for non-EDDA data. In another example, if atwo bit scheduling request is utilized, the network may assume the SR isfor high priority data, for example if use of the two bit SR is reservedfor high priority data.

For the examples above, a first priority level may be a higher prioritylevel, (e.g., related to measurement reports, if configured, or forconversational services, and the like). A second priority level may be alower priority level, for example, related to intermittent traffic frombackground applications. When the above methods are used such that afirst priority may indicate a high priority level, the network mayhandle legacy access requests in the same manner, for example, with thesame equal priority, while providing enhanced service to requests thatuse the indication of high priority. When the above methods are usedsuch that a first priority may indicate a low priority level, thenetwork may handle legacy requests in the same manner, for example,while WTRUs implementing such methods may provide opportunities for thenetwork to handle low priority service requests on a best-effort basis.

For the examples above, the WTRU may use such methods for the randomaccess procedure for a specific set of DRB while the WTRU is in aRRC_CONNECTED state, or for a specific type of RAB (e.g., conversationalRAB in the case of high priority) for the NAS Service Request while theWTRU is in a RRC_IDLE state, or for a specific application (e.g., avoice service in the case of high priority).

If the WTRU determines that a Random Access procedure should beinitiated based on a higher priority level while there may already beone random access procedure ongoing for a lower priority level, the WTRUmay abort the ongoing procedure and initiate a new Random Accessprocedure with a different set of parameters, for example, according tothe higher priority level.

The WTRU may determine that the serving cell on whose resources the WTRUmay be performing a random access is in a congested state whenperforming a random access procedure. The WTRU may perform UnsuccessfulRAR reception or Successful RAR reception in this scenario. Combinationsof Unsuccessful RAR reception and Successful RAR reception may be usedto indicate different levels of congestion and/or a specific backoffperiod.

If the WTRU does not successfully receive a RAR during a RACH procedure(e.g., after a threshold or maximum number of preamble retransmissions),the WTRU may determine a congestion state of a serving cell as afunction of the preamble transmissions, for example, whether legacy or amethod disclosed herein, and as a function of whether or not a RAR isreceived. The WTRU may monitor PDCCH for downlink control signalingscrambled with RA-RNTI according to the transmitted preamble for a RARreception. The WTRU may not determine that it has successfully receiveda RAR for the corresponding preamble, and the WTRU may have performedthe maximum number of preamble transmissions for this random procedure.

If the WTRU used a method different than the legacy R8 method for thetransmission of the preamble for the random access procedure, forexample according to one or more of the methods disclosed herein such asindicating a priority level, the WTRU may determine that the servingcell may be in a congested state. The WTRU may perform one or moreactions disclosed herein for responding to congestion. For example, ifthe WTRU transmits a preamble in a manner that indicates a high prioritylevel (e.g., using a specific preamble, using a specific PRACHoccasion/opportunity, indicating priority in the SR, etc.), and the WTRUdoes not receive a RAR, the WTRU may determine that the network is in acongested state.

Furthermore, when the WTRU does not detect PR-RNTI for a given period oftime, the WTRU may cancel the corresponding SR for congestion control.The WTRU may initiate a normal SR, for example if the SR is being usedto manage uplink resources.

For Successful RAR reception, if the WTRU transmitted a preamble, forexample, according to one or more of the methods disclosed herein, theWTRU may determine a congestion state of a serving cell based on thereceived RAR and/or the preamble transmission. For example, the RAR mayimplicitly (e.g., when interpreted in light of the preamble transmissionmethod or some other network parameter) or explicitly indicate thecongestion state. As an example, the WTRU may determine a congestionstate based on the RNTI used to decode the RAR (e.g., RA-RNTI, PR-RNTI,etc.) the reception window of RAR, the temporary C-RNTI included in theRAR (e.g., the temporary C-RNTI may indicate congestion), the backoffindicator (BI) in the RAR, an indication in a padding region of a RAR,and/or the like.

In the examples disclosed herein, a general expression for calculationof a RA-RNTI′ may be:RA-RNTI′=1+t_id+10*f_id  (2)Additionally, an offset value may be added to the legacy RA-RNTIcalculation, for example so that the network may indicate a prioritylevel and/or respond to a specific type of preamble transmission. Forexample, the RA-RNTI′ may be determined as:RA-RNTI′=1+t_id+10*f_id+offset_value  (3)The value of offset_value may be known and/or configured, or may be afunction of the method used for the preamble transmission as describedabove. For example, the offset_value may correspond to/be associatedwith a given preamble value, a preamble index, a preamble type, apreamble group, a PRACH index, a PRACH opportunity, and/or the like.

For RA-RNTI of the RAR, once the WTRU has transmitted a preamble, theWTRU may decode PDCCH to determine scheduling information for a RARusing a plurality of RNTI values, where one or more values may indicatea congested state (e.g., RA-RNTI′). For example, for a given preambletransmission, the WTRU may determine a first RA-RNTI′ such that if a RARis successfully decoded with the first RA-RNTI′ (e.g., an RNTI valueassociated with the transmitted preamble), the WTRU may determine thatthe cell is in a congested state.

The WTRU may determine a congestion state based on the reception windowfor a RAR. For example, once the WTRU has transmitted a preamble, theWTRU may decode the PDCCH to determine scheduling information for a RARusing a plurality of RAR windows that may be non-overlapping, wheresuccessful reception of a RAR in one or more windows may indicate acongested state. For example, for a given preamble transmission, theWTRU may decode RA-RNTI (e.g., and/or RA-RNTI′) in a first window. If noRAR may be received in the first window, the WTRU may additionallydecode RA-RNTI in a second window. If a RAR that may correspond to thepreamble transmitted may be successfully received in the second window,the WTRU may determine that the cell is in a congested state.

For Temporary C-RNTI in RAR indicating congestion (e.g., using aspecific codepoint) once the WTRU may have transmitted a preamble, theWTRU may decode the PDCCH to determine scheduling information for a RAR,where successful reception of a RAR with the Temporary C-RNTI field maybe set to a specific codepoint. For example, for a preamble transmissionaccording to a method described herein, if the WTRU successfullyreceives a RAR that may correspond to the preamble transmitted and theTemporary C-RNTI field is set to a configured or known codepoint (e.g.,all zeroes) the WTRU may determine that the cell is in a congestedstate. As another example, if the WTRU successfully receives a RARaccording to one of the methods described herein, for example, bydecoding for RAR using a plurality of RA-RNTIs and/or using a pluralityof reception windows, with the Temporary C-RNTI field set to aconfigured or known codepoint (e.g., all zeroes), the WTRU may determinethat the cell is in a congested state.

For backoff indicator (BI) in the RAR, once the WTRU has transmitted apreamble, the WTRU may decode the PDCCH to determine schedulinginformation for a RAR, where successful reception of a RAR with the BIfield set may indicate a congested state. For example, for a preambletransmission according to a method disclosed herein, if the WTRUsuccessfully receives a RAR that may correspond to the preambletransmitted and the BI field is set, the WTRU may determine that thecell is in a congested state. As another example, if the WTRUsuccessfully receives a RAR according to one of the methods disclosedherein, for example, by decoding for RAR using a plurality of RA-RNTIand/or using a plurality of reception windows and/or with TemporaryC-RNTI set to a specific codepoint, with the BI field set in the RAR,the WTRU may determine that the cell is in a congested state.

For Indication in the padding region of a RAR, once the WTRU may havetransmitted a preamble, the WTRU may decode the PDCCH to determinescheduling information for a RAR, where successful reception of a RARwith additional information in the padding region may indicate acongested state. For example, if the WTRU successfully receives a RARthat may correspond to the preamble transmitted and with additionalinformation, for example, a new field, in the padding region, the WTRUmay determine that the cell is in a congested state.

For reception of a Scheduling Request (SR) response, the PDCCH maycontain a zero size uplink grant as a response to a low priorityscheduling request transmitted by the WTRU. When the WTRU may receivethis type of response as a result of transmitting SR for low prioritydata, the WTRU may implicitly assume that the network is congested andmay not try to access the network for a certain period of time or mayexecute one or more methods disclosed herein.

For reception of an SR response, when the WTRU may transmit an SRrequest for low priority data, the WTRU may start monitoring the PDCCHin a number of subframes (e.g., every subframe). The WTRU may monitorfor DCI types 0 scrambled with a specific subframe with its RNTI for theuplink grant and another specific RNTI, for example, EDDA-RNTI. If theWTRU can decode the grant with EDDA-RNTI, it may indicate to the WTRUthat the network may be congested, and the WTRU may take actions asdescribed herein. It may be possible that this EDDA-RNTI may be a groupRNTI assigned to more than one WTRU. Any able that can decode any DCIfrom an eNB using this RNTI may discover that the network may becongested.

If the WTRU may determine that the serving cell on whose resources it isperforming a random access procedure may be in a congested state, forexample, according to any of the methods disclosed herein, the WTRU mayperform one or more of the procedures disclosed herein.

For example, the WTRU may abort the NAS Service Request (NAS SR) if aNAS SR procedure is ongoing. The WTRU may abort an ongoing RRC procedurefor a transition to a CONNECTED state, if the WTRU is not already in theCONNECTED state. The WTRU may abort an ongoing RRC connectionestablishment procedure, if the WTRU is not already in the CONNECTEDstate. The WTRU may cancel transmission of, and/or discard, dataassociated with the event that triggered the random access procedure(e.g., after a certain amount of time).

The WTRU may apply a backoff period before attempting another access,for example, after a configured amount of time. The WTRU may initiate acell reselection procedure with a different offset (e.g., a loweracceptable threshold for cell reselection) such that a different cell(e.g., with less congestion but lower quality) may be selected as aresult. The WTRU may perform additional measurements, for example, if noRAR was received, to determine whether or not the failure to receive aRAR was due to cell congestion or due to poor radio link quality.

The WTRU may initiate an alternative transmission method for theconsidered data (e.g., a connectionless approach) a contention-basedPUSCH transmission, or the like. The WTRU may initiate the use of adormant behavior (e.g., a transition to a dormant mode). The WTRU maydetermine that the serving cell may be congested and that the WTRU maynot be experiencing uplink radio link failure.

The PR-RNTI may be revoked when the WTRU may reselect to a differentcell. For example, the PR-RNTI may be revoked if the PR-RNTI may bevalid in an idle mode and/or when the WTRU may move to the idle mode, ifthe PR-RNTI may be valid in a connected mode.

In an example, a WTRU may receive a configuration described herein viadedicated signaling or from the broadcasted system information, or by acombination of both. RACH parameters may be specific to a set of PRACHresources. In an example, a WTRU may be configured with one or moreparameters for the random access procedure that are specific to a secondset of PRACH resources. The WTRU may use these parameters for a preambletransmission using a resource of the concerned set.

For example, a WTRU may be configured with a value for one or more ofthe following parameters, which value may be specific to a specific setof PRACH resources. For example, a WTRU may be configured with a valuefor the maximum number of preamble transmission (e.g., preambleTransMax)for a preamble transmission on a resource of a second set of PRACHresources. For example, the value for the second set may be configuredsuch that it is smaller than that of a first set for the purpose oflimiting the amount of retransmissions on the second set. In an example,a WTRU may be configured with a value for the size of the Random AccessResponse (RAR) window (e.g., Ra-ResponseWindowSize) for the reception ofa RAR corresponding to a preamble transmission on a resource of a secondset of PRACH resources. For example, the value for the second set may beconfigured such that it is larger than that of a first set for thepurpose of allowing more flexibility in time for scheduling a RAR.

In an example, a WTRU may be configured with a value for the initialpreamble power (e.g., preambleInitialReceivedTargetPower) for a preambletransmission on a resource of a second set of PRACH resources. Forexample, if the second set uses a different preamble format (e.g., onewith a less robust encoding) than that of a first set, the WTRU may beconfigured with a value that is larger than that of the first set (e.g.,the cell-specific set) for the purpose of improving the reception of thepreamble at the receiver. The WTRU may use a value (or an offset derivedtherefrom) that corresponds to a previous transmission in this cell, if,for example, the estimated downlink path loss has not changed by morethan a threshold value (e.g., in dB).

In an example, a WTRU may apply a power offset to the preambletransmission (e.g., DELTA_PREAMBLE), for example, if the second set usesa different preamble format than that of a first set. In an example, aWTRU may be configured with the set of preambles available for theconcerned set of PRACH resources, for example, if they differ betweenthe first and second set. For example, the set of preambles for a secondset of resources may correspond to a subset of the preambles availablefor a first set. In an example, a WTRU may be configured with the powerramping step (e.g., powerRampingStep) for a set of PRACH resources. Forexample, the WTRU may apply a different power ramping step whenperforming preamble retransmissions for a second set of PRACH resourcesthan when performing preamble retransmission using a first set of PRACHresources.

In an example, a WTRU may be configured with a dedicated preamble for aset of PRACH resources. For example, the WTRU may be configured with adedicated preamble that the WTRU may use for a preamble transmission fora RACH procedure using a second set of PRACH resources. For example,when the resources of a second set are mutually exclusive in relation toany other set of PRACH resources configured for the WTRU, the WTRU maybe configured with a RACH dedicated RACH preamble for the second set.For example, the preamble may be derived according to a method ormethods described herein.

In an example, a WTRU may be configured with the backoff period to beused with a set of PRACH resources. For example, the WTRU may apply alonger backoff period for a RACH procedure using a second set ofresources than when using a first set of PRACH resources. Such a schememay, for example, be used to configure a WTRU such that the powersettings for a preamble transmission using a second set of PRACHresources may be either more aggressive or more conservative than for atransmission on a first set of resources, for example, by settingdifferent initial power setting and/or a different power ramping.

A WTRU may be configured to initiate a second Random Access procedurewhile a first random access procedure may already be ongoing. Forexample, in LTE, the WTRU implementation may determine whether or not toabort an ongoing RACH procedure when a second RACH procedure istriggered in the same serving cell (e.g., using a single set of PRACHresources). A WTRU configured with a plurality of sets of PRACHresources may implement a priority between an ongoing RACH procedure fora specific set of PRACH resources and a trigger to initiate a RACHprocedure using a different set of PRACH resources. This priority may bebased on the relative priority level of the concerned set of PRACHresources and/or the trigger by which the WTRU determined that it shouldperform a RACH procedure.

For example, the WTRU may abort an ongoing RACH procedure for which apreamble was transmitted on the PRACH resources of a second set (e.g., aset that may correspond to a RA-SR procedure for data of lower priority)based on the WTRU determining that a RACH procedure should be initiatedusing the PRACH resources of a first set (e.g., a set that maycorrespond to a RA-SR procedure for data of higher priority). Afteraborting the ongoing RACH procedure, the WTRU may initiate a RACHprocedure using the resources of the first set as a new procedure, forexample, by resetting the number of preamble transmissions, by selectinga preamble (e.g., a dedicated preamble) that corresponds to the firstset of PRACH resources, and/or by using the corresponding set ofparameters.

In an example, a WTRU may transmit the first preamble for the new RACHprocedure using the power level of the last preamble transmission of theRACH procedure that was aborted. In an example, a WTRU may transmit thefirst preamble for the new RACH procedure using the power level of thelast preamble transmission of the RACH procedure that was aborted forthe last preamble transmission for which the corresponding RAR windowhad expired when the WTRU determined to abort the ongoing RACHprocedure.

In an example, the WTRU may receive a configuration and may determine anumber/identity of additional PRACH resources according one or more ofthe following methods. For example, a WTRU may determine anumber/identity of PRACH resources such that the PRACH resources may beadded and/or multiplexed in the time domain. For example, a WTRU mayreceive a configuration with a plurality of prach-ConfigIndex IEs. EachIE may correspond to a different set of PRACH resources and may includea time domain configuration the different set of PRACH resources. Forexample, a WTRU may determine a number/identity of PRACH resources suchthat the PRACH resources may be added and/or multiplexed in thefrequency domain. For example, a WTRU may determine a number/identity ofPRACH resources using configuration messages, and the WTRU may receive aconfiguration with a plurality of prach-FreqOffset IEs. Each IE maycorrespond to a different set of PRACH resources and may include afrequency domain configuration the different set of PRACH resources.Frequency multiplexing may limit the maximum data rate for thecorresponding subframe because frequency multiplexing may make themaximum number of consecutive PUSCH PRBs smaller. However, a slower datarate may be less of a concern with a second set of PRACH resources withlow-density and/or possibly spread in time.

In an example, PRACH resources may be added and/or multiplexed in boththe time and the frequency domains. For example, using configurationmessages the WTRU may receive a configuration with a plurality ofprach-Config IEs and prach-FreqOffset IEs. The sets of IEs maycorrespond to different sets of PRACH resources and may include a timeand/or frequency domain configuration the different sets of PRACHresources.

Time multiplexing, frequency multiplexing, and/or time and frequencymultiplexing may be used to add and/or multiplex additionalcell-specific PRACH resources (e.g., using signaling on the broadcastchannel and/or other system information) and/or as WTRU-specificconfigurations (e.g., identical for a plurality of WTRUs in the samecell). Time multiplexing, frequency multiplexing, and/or time andfrequency multiplexing may be used to extend an existing PRACH. Forexample, a WTRU may use the same set of preambles (e.g., the same valuefor rootSequenceIndex may be applicable to each of the sets PRACHresources) and/or the same preamble format (e.g., the same value for thepreamble format as indicated by the prach-ConfigurationIndex may beapplicable to each of the sets of PRACH resources) for the transmissionof a preamble in the additional PRACH resources. Time multiplexing,frequency multiplexing, and/or time and frequency multiplexing may beused to configure one or more additional PRACH resources, for examplefor which a WTRU may use a different set of preambles and/or a differentpreamble format for the transmission of a preamble in the additionalPRACH resources.

In an example, configuration messages may be utilized to assist a WTRUin determining additional PRACH resources based on a state of the WTRU(e.g., whether or not the WTRU is configured to use a dormant behavior)and/or based on whether or not the WTRU received the configuration usingdedicated signaling. For example, if the configuration was received viadedicated signaling, a WTRU may use a different interpretation of thePRACH configuration, for example, using an alternative (and/or extended)mapping table corresponding to the prach-ConfigIndex value.

The WTRU may determine the one or more set(s) of PRACH resources basedon one or more of a number of criteria. In an example, the WTRU maydetermine one or more set(s) of PRACH resources based on a PRACHconfiguration. For example, a second set of PRACH resources maycorrespond to at least part of the PRACH resources added and/ormultiplexed for the second PRACH configuration. For example, the WTRUmay determine that PRACH resources configured in addition to the PRACHresources available to a SPUE correspond to the resources of a secondset of PRACH resources. Such a method may allow the network to emulate aplurality of PRACH configurations (e.g., to handle contention betweenMPUEs and SPUEs in a given cell).

In an example, the WTRU may determine one or more set(s) of PRACHresources based on a System Frame Number (SFN). For example, a secondset of resources may be determined as a function of the SFN. Forexample, the WTRU may be configured with a periodicity X such thatresources corresponding to a second set include one or more PRACHoccasions within a frame for which SFN mod(X)=0. Example values for Xmay be configured to approximate the maximum latency for the lowpriority services for a WTRU operating with a dormant behavior. In anexample, SFN periodicity may be used in combination with a PRACH MaskIndex, as described herein. SFN periodicity may be applicable to theinitial preamble transmission for a given RACH procedure. Otherresources may be determined as a function of the PRACH occasion for theinitial preamble transmission, as described herein. This method may beused by the network to implement time-division for PRACH such thatcontention between MPUEs and SPUEs in a given cell may be reduced orminimized.

In an example, the WTRU may determine one or more set(s) of PRACHresources based on Start of DRX On-Duration (e.g., drxStartOffset). Forexample, a second set of PRACH resources may be determined as a functionof the start of the DRX On-Duration period, if configured. Examplevalues for the DRX cycle length may be configured to approximate themaximum latency for the low priority services for a WTRU operating witha dormant behavior. If multiple DRX configuration and or DRX cycles maybe supported by the MPUE, the MPUE may use the start of the DRXOn-Duration period that may correspond to the active DRX configurationand the current DRX cycle to determine one or more resources of thesecond set of PRACH resources.

For example, the WTRU may be configured with DRX and may determine thatresources corresponding to a second set may include any PRACH occasionscorresponding to a subframe that is part of the DRX On-Duration periodin a DRX cycle. In an example, if the WTRU fails to receive the RACHMSG2 message successfully and cannot perform a preamble retransmissionwithin the concerned On-Duration period as it has either expired and/orthere are no PRACH occasions left in said period, the WTRU may determinethat the RACH procedure is unsuccessful.

For example, the WTRU may be configured with DRX and may determine thatresources corresponding to a second set may include the first PRACHoccasion starting from the first subframe for which the WTRU is in DRXActive Time at the beginning of the On-Duration period in a DRX cycle.Such a scheme may be used for the initial preamble transmission to limitthe rate of initial preamble transmission. In an example, preambleretransmissions may use a resource determined according a differentmethod, for example, as a function of the PRACH occasion used for theinitial preamble transmission for a RACH procedure. In an example,preamble retransmission may use any PRACH resources. In an example, ifthe WTRU fails to receive the RACH MSG2 message successfully and cannotperform a preamble retransmission within the PRACH occasions associatedwith the concerned On-Duration period, the WTRU may determine that theRACH procedure is unsuccessful. This method may be used in combinationwith a PRACH Mask Index, as described herein. This method may be used tolimit the rate of initial preamble transmission.

In an example, a WTRU may determine one or more set(s) of PRACHresources based on a Semi-static PRACH Mask Index. For example, a secondset of PRACH resources may correspond to a configuration of a PRACH MaskIndex (e.g., for an index with a nonzero value). For example, the WTRUmay be configured with a semi-static PRACH Mask Index corresponding to asecond set of PRACH resources.

In an example, the masking method may be extended such that it may applyto multiple frames, for example, in combination with SFN numbering. Forexample, a WTRU may receive PRACH mask information such as an indexvalue (e.g., an index value such as index value 1 which may indicatePRACH Resource Index 0 in any 10 ms frame for a SPUE) for a second setof resources. The mask may be applicable in frames for which SFN mod X=0(e.g., X ms periodicity). The MPUE may then use this resource for aPRACH transmissions corresponding to a second set of resources in aframe that meets the SFN timing criteria. In other frames, the WTRU mayuse the resource for a preamble transmission that may correspond to thefirst set of resources.

In an example, the masking method may be extended such that more valuesmay be signaled for SPUEs. In an example, the masking method may use analternative table of values for MPUEs than is used for SPUEs. Thenetwork may use alternate masking tables to implement time- and/orfrequency-division for the PRACH resources of a cell such thatcontention between MPUEs and SPUEs may be reduced or minimized.

In an example, a WTRU may determine one or more set(s) of PRACHresources based on DRX On-Duration period. For example, a second set ofresources may be determined as a function of the DRX On-Duration period.For example, a WTRU may be configured with DRX and may determine thatresources corresponding to a second set of PRACH resources may includeone or more PRACH occasions that correspond to a subframe that may bepart of the On-Duration period of the DRX cycle. In an example, a WTRUmay determine one or more set(s) of PRACH resources based on DRXOn-Duration period in combination with a configured PRACH Mask Index.For example, the resources of the second set may be the PRACH occasionsthat correspond to the logical AND combination of the PRACH masking andthe subframes that are part of the DRX On-Duration period. In anexample, a WTRU may determine that the resources of the second set maybe the PRACH occasions that correspond to the logical AND combination ofthe PRACH masking and the subframes that are part of the DRX On-Durationperiod for the initial preamble transmission, but not for subsequenttransmissions. In this example, preamble retransmissions may use aresource determined according one of the other methods disclosed herein,for example as a function of the PRACH occasion used for the initialpreamble transmission for a RACH procedure.

In an example, a WTRU may be configured with PRACH resources, and thePRACH resources may be common to any preamble transmission. The secondset of resources may include a dedicated preamble. In an example, theWTRU may transmit the dedicated preamble in a PRACH opportunity that maycorrespond to a subframe for which the WTRU is in DRX Active Time (e.g.,D-SR replacement) during the DRX On-Duration period (e.g., which is afunction of the SFN and active cycle). The reception of PDCCH signalingmay be considered as successful reception of the RACH MSG2 message.Failure to receive the RACH MSG2 message successfully before the end ofthe On-Duration period may trigger the WTRU to determine that the RACHprocedure is unsuccessful. The network may implement such a method inorder to implement time- and/or frequency-division for the PRACHresources of a cell such that contention between MPUEs and SPUEs may bereduced or minimized.

In an example, a WTRU may determine one or more set(s) of PRACHresources based on DRX Active Time. For example, a second set of PRACHresources may be determined as a function of the DRX Active Time. Forexample, the WTRU may be configured with DRX and may determine thatresources corresponding to a second set include one or more PRACHoccasions that may correspond to one or more subframes that are part ofthe DRX Active Time for the WTRU. In an example, original preambletransmission may utilize PRACH resources for transmission based on DRXactive time, but preamble retransmissions may use some other method. Inan example, preamble retransmissions may use a resource determinedaccording to any of the methods described herein, for example as afunction of the PRACH occasion used for the initial preambletransmission for a RACH procedure. In an example, preambleretransmission may use any PRACH resources. In an example, determiningthe PRACH transmission parameters may be based on DRX Active Time incombination with a configured PRACH Mask Index. In this case, theresources of the second set may be the PRACH occasions that correspondto the logical AND combination of the PRACH masking and the subframesthat are part of the DRX Active Time.

For example, a WTRU may be configured with PRACH resources, and theconfigured PRACH resources may be common to any preamble transmission.The second set of resources may include a dedicated preamble. The WTRUmay transmit the dedicated preamble in a PRACH opportunity that maycorrespond to a subframe for which the WTRU is in DRX Active Time (e.g.,D-SR replacement), but may refrain from doing so in other subframes. Inan example, the reception of PDCCH signaling may be considered assuccessful reception of the RACH MSG2 message. In an example, failure toreceive the RACH MSG2 message successfully before the end of the DRXActive Time may trigger the WTRU to determine that the RACH procedure isunsuccessful. Such a method may allow the use of a period subsequent tothe transmission of a burst by which a WTRU may request furtherresources, for example in case the burst did not correspond to abackground application.

In an example, a WTRU may determine one or more set(s) of PRACHresources based on the PRACH occasion used for the initial preambletransmission for a RACH procedure. For example, a second set of PRACHresources may be determined as a function of the PRACH occasion of aninitial preamble transmission for an ongoing RACH procedure. In anexample, a WTRU may determine additional PRACH resources for a secondset of resources (e.g., for retransmissions) according to one or more ofthe following. For example, starting from the initial preambletransmission, and up to the maximum number of preamble transmissions forthe concerned RACH procedure, the WTRU may transmit a preamble in aPRACH resource such that the resources may correspond to any of theresources configured for the WTRU, the resources may correspond to anyof the resources of a second set configured for the WTRU, and/or theresources may be indicated by a PRACH Mask Index. Such a scheme may beused to limit the rate of initial preamble transmission.

In an example, a WTRU may determine one or more set(s) of PRACHresources based on Configuration of density. For example, a second setof PRACH resources may be determined as a function of a density signaledfor the second set of PRACH resources. For example, for FDD and TDD, theWTRU may determine that for a PRACH occasion with a plurality of PRACHopportunities, the opportunity with the lowest index in the subframe maycorrespond to a first set of resources while other PRACH opportunitiesin the subframe may correspond to a second set. Such a scheme may beused to minimize signaling overhead when configuring additional PRACHresources, and may allow the network to configure PRACH resources as afunction of the desired density in a frame. Such a scheme may allow theWTRU to identify a second set of PRACH resources, for example, based onan identification of a second set corresponding to the additionaldensification.

A WTRU determining one or more set(s) of PRACH resources based onparameters or criteria may be used to increase resource utilization. Forexample, PRACH partitioning may allow the reuse of the PRBs associatedwith a second set of resources such that PUSCH transmission may also bescheduled in the corresponding PRBs, for example, as a function of theprobability of collision with a preamble transmission. In an example,the probability of collision may be a function of the number of WTRUs inthe cell that may use the second set of resources.

The network may coordinate the configured sets of allocated PRACHresources (e.g., the first set and/or the second set) such that each ofthe configured sets are mutually exclusive (e.g., there may be nooverlap between the PRACH resources associated with the first set andthe PRACH resources associated with the second set). However, in anexample, there may be overlap between the PRACH resources associatedwith the first set and the PRACH resources associated with the secondset.

If one or more PRACH resources are configured as part of a plurality ofsets (e.g., the same PRACH resource may be indicated as available in afirst and in a second set), the WTRU may use the corresponding PRACHresource when the WTRU determines that a preamble transmission should beperformed in a PRACH resource. If one or more PRACH resources overlapbetween a plurality of PRACH resource sets, in an example, the WTRU maydetermine that the overlapping resource may be used for any of theconcerned sets. For example, the PRACH resource may be used when aresource from any of the concerned sets is to be used. In an example, ifthe same preamble format is used for the transmission of a preamble inthe PRACH resource that is part of both sets irrespective of which setis to be used, the WTRU may determine that the resource may be used foreither of the sets.

In an example, if one or more PRACH resources overlap between aplurality of PRACH resource sets, the WTRU may determine the PRACHresource that overlaps may be used for the first set, but not for thesecond set. For example, the WTRU may determine that the overlappedPRACH resource should be considered part of the first set of PRACHresources, for example for use with data and/or events of higherpriority. In an example, the WTRU may determine that the overlappedPRACH resource may not be used for both sets if different preambleformats are used for the transmission of a preamble for the concernedsets.

In an example, if one or more PRACH resources overlap between aplurality of PRACH resource sets, the WTRU may determine the PRACHresource that overlaps may be used for the second set, but not for thefirst set. For example, the WTRU may determine that the overlapped PRACHresource should be considered part of the second set of PRACH resources,for example for data and/or an event of lower priority. In an example,the WTRU may determine that the overlapped PRACH resource may not beused for both sets if different preamble formats are used for thetransmission of a preamble for the concerned sets.

A WTRU may be configured to determine a second set of PRACH preambles,for example, for use with a second set of PRACH resources. For example,the WTRU may determine the set of preambles available for a second setof PRACH resources according to one or more methods disclosed herein.

In an example, a WTRU may be configured to determine a second set ofPRACH preambles based on a root sequence (e.g., rootSequenceIndex)specific to a second set of PRACH resources. For example, the WTRU maybe configured with a root sequence index for the second set that may bedifferent from that of the first set. For example, the WTRU may derive asecond set of preambles applicable to a second set of PRACH resourcesusing a root sequence that may be specific to the concerned set of PRACHresources. In an example, the WTRU may determine to utilize the secondset of preambles and/or the second root sequence for the second set ofPRACH resources based on a determination that the PRBs that correspondto the second set of PRACH resources are mutually exclusive to the setof PRBs that corresponds to a first set of PRACH resources.

In an example, a WTRU may be configured to determine a second set ofPRACH preambles based on a subset of preambles from a first set. Forexample, a WTRU may be configured to determine a second set of PRACHpreambles based on a subset of the cell-specific configuration. In anexample, the WTRU may determine that a subset of the preambles availablefor the serving cell and/or first set of PRACH resources may be used fora preamble transmission on a second set of PRACH resources. The WTRU maydetermine the identity of the subset of preambles according to one ormore of a number of parameters.

In an example, a WTRU may be configured to determine the identity of thesubset of preambles that may be used for the second set of PRACHresources based on the WTRU being configured with a dedicated preamblefor the second set of PRACH resources. In an example, a WTRU may beconfigured to determine the identity of the subset of preambles that maybe used for the second set of PRACH resources based on a configurationof the preamble group that may specify which random access procedures(and/or triggers) are applicable to certain preambles. For example, theWTRU may be configured such that a RA-SR procedure may use a second setof PRACH resources. The preambles applicable to the function or triggermay be determined based on a time-division of the preamble assignmentsin a serving cell. For example, SPUEs may be configured according toexisting methods. For example, MPUEs may be configured with a randomaccess configuration that includes the parameters that may be indicativeof preamble grouping. For example, the configuration may identify whichpreambles are applicable to a second set of PRACH resources. Such ascheme may be used when such resources may be mutually exclusive in timewith resources available to SPUEs in the same cell.

In an example, a WTRU may be configured to determine a subset ofpreambles to be used with a second set of PRACH resources based onpreamble group-division of preamble assignments in a serving cell. In anexample, preamble grouping (e.g., preamble group C of FIG. 7) may beachieved according to various criteria. For example, preamble groupingmay be based on a preamble configuration as seen by the network. Forexample, both cell-specific and WTRU-specific preambles may be groupedbased on a preamble configuration as seen by the network. In an example,the network may reserve a number of preambles for use by MPUEs, and inan example the preambles reserved for MPUEs may not be used by SPUEs.For example, the network may reserve a group of preambles (e.g.,preamble group C of FIG. 7) of sizeOfRA-PreambleGroupC for a given setof PRACH resources in a serving cell. FIG. 7 illustrates preamblegrouping in an example configuration 700 for distributing RACHpreambles.

For example, there may be 64 possible preambles 702. The network mayconfigure SPUEs 704 with up to 64-sizeOfRA-PreambleGroupC preambles. TheSPUEs 704 preambles may be spread across group A and group B (ifconfigured), for example, according to R10 methods.

The network may then also configure MPUEs 706 with up to 64 preambles,which may be spread across group A, group B, group C, and/or anycombination thereof. For example, a plurality of preambles may be spreadacross group A and group B (if configured) according to R10 methods,with additionally up to sizeOfRA-PreambleGroupC preambles in group C. Inan example, a WTRU may be configured with a set of preambles that may beselected for transmission in the second set of PRACH resources, but notin the first set of PRACH resources.

In an example, preamble grouping may be based on a preambleconfiguration as seen by the WTRU. For example, a SPUE 704 may beconfigured according to existing methods, and a MPUE 706 may beconfigured with additional parameters such that the MPUE 706 may derivean additional group of preambles. When the WTRU may select a preamblefor a transmission for data and/or events that correspond to a secondset of PRACH resources, the WTRU may select a preamble in group C forthe corresponding resource.

In an example, a SPUE 704 may be configured such thatsizeOfRA-PreambleGroupA≦numberOfRA-Preambles. For example, preambles ingroup A may be each of the available preamble, for example if group B isnot configured. However, if group B is configured for a SPUE, thePreamble Group A may range from preamble index [0,sizeOfRA-PreamblesGroupA−1], and Preamble Group B may range from index[sizeOfRA-PreamblesGroupA, numberOfRA-Preambles−1]. In an example, thenetwork may allocate preambles such that the total number of preambles702 available to the SPUEs 704 may be less than 64. For example, thenumber of preambles allocated to SPUEs 704 may be the difference betweenthe total number of preambles and the number of preambles to beallocated to WTRUs that may support additional behavior for randomaccess procedure (e.g., MPUEs 706). For example:numberOfRA-Preambles (SPUE)+sizeOfRA-PreambleGroupC (MPUE)≦64  (4)In an example, a SPUE may not be configured with a value forsizeOfRA-PreambleGroupC, and instead may be configured with theparameter numberOfRA-Preambles.

In an example, an MPUE 706 may be configured with specific preambles.For example, an MPUE 706 may be configured with a number of randomaccess preambles that may be available for the MPUE 706 in the givencell. For example, an MPUE 706 may be configured with a number ofadditional preambles (e.g., sizeOfRA-PreambleGroupC), from which theWTRU may implicitly determine the maximum number of preambles available.In an example, an MPUE 706 may be configured with a value (e.g.,numberOfRA-PreamblesMPUE) that may supersede that of the parameternumberOfRA-Preambles. For example, an MPUE 706 may be configured with avalue (e.g., numberOfRA-PreamblesMPUE) that may supersede that of theparameter numberOfRA-Preambles as common configuration information forthe cell. The common configuration information for the cell may bereceived from broadcasted system information and/or by dedicatedsignaling in a common configuration (e.g., RACH-ConfigCommon).

If a MPUE 706 is configured with a value (e.g.,numberOfRA-PreamblesMPUE), the WTRU may derive the value forsizeOfRA-PreambleGroupC, for example usingnumberOfRA-PreamblesMPUE−numberOfRA-Preambles. The total number ofpreambles available may be equal to or less than 64. For example,numberOfRA-Preambles+sizeOfRA-PreambleGroupC may represent the totalnumber of preambles. In an example, numberOfRA-PreamblesMPUE mayrepresent the total number of available preambles. An MPUE 706 may beconfigured with a non-zero preamble group B, for example, where:sizeOfRA-PreambleGroupA≦numberOfRA-PreamblesMPUE−sizeOfRA-PreambleGroupC  (5)

In an example, if a preamble group B exists, then an MPUE 706 may beconfigured such that the ranges of the groups of preambles may be:

Preamble Group A: [0, sizeOfRA-PreamblesGroupA−1];

Preamble Group B: [sizeOfRA-PreamblesGroupA, numberOfRA-Preambles−1];

Preamble Group C: [numberOfRA-Preambles,numberOfRA-Preambles+sizeOfRA-PreambleGroupC−1].

In an example, if a preamble group B exists, then an MPUE 706 may beconfigured such that the ranges of the groups of preambles may be:

Preamble Group A: [0, sizeOfRA-PreamblesGroupA−1];

Preamble Group B: [sizeOfRA-PreamblesGroupA,numberOfRA-PreamblesMPUE−numberOfRA-Preambles−1];

Preamble Group C: [numberOfRA-PreamblesMPUE−numberOfRA-Preambles,numberOfRA-PreamblesMPUE−1].

If Group B is not configured, the last sizeOfRA-PreambleGroupC preamblesof the total number of available preambles may correspond to preamblegroup C. Preamble grouping where one group of preambles may be dedicatedto a second set of PRACH resources may be used to limit contentionbetween SPUEs 704 and MPUEs 706. Grouping preambles may be used incombination with other methods described herein. For example, groupingpreambles may be used in combination with a PRACH Mask Index.

A WTRU may be configured such that the preamble format that maycorrespond to a second set of PRACH resources may use a differentsequence length than that of a first set. For example, the WTRU may usea longer T_(seq) (e.g., 1.6 ms) to transmit more than 6 bits of preambleinformation. In an example, the WTRU may include two different sequencesin the preamble format, where each sequence may be of equal length(e.g., 0.8 ms in length). In an example, a second sequence may beincluded when the WTRU uses a longer preamble format (e.g., a 2 ms or 3ms preamble). For example, the WTRU may use a preamble format that isspecific to the concerned set of PRACH resources, and the format may beassociated with a longer sequence length.

For example, the WTRU may use the additional T_(seq) length to extendthe range of the preamble space. Extending the sequence length and/orextending the range of the preamble space may be used to multiplexmultiple MPUEs 706 in the same (e.g., and/or small or limited) set ofPRACH resources spread in time. For example, an extended sequence lengthand/or an extended range of the preamble space may be used incombination with methods that limit the rate of initial preambletransmission. For example, such a scheme may allow multiple populationsof WTRUs to share the same set of PRACH resources. The shared set ofresources may be used for RACH procedures of lower priority while usinga dedicated preamble to emulate a dedicated PRACH with relaxed latencyrequirements.

In LTE, for preamble format 2 and 3, the sequence (0.8 ms) may berepeated once in the transmission of the preamble. Formats 2 and 3 maybe used to ensure that the receiver may receive a sufficient amount ofenergy, for example in the case of large cell deployment. Formats 2 and3 may use a larger cyclic prefixes. In an example, instead of repeatingthe same sequence, a WTRU may be configured use a second sequence in thepreamble format, such that the WTRU may provide additional informationin the transmission of a preamble. For example, the additionalinformation may include the priority of the random access procedure. Forexample, the additional information may include the amount of data thatis available in the buffer of the WTRU for transmission. For example,the additional information may include an identity of the WTRU thatperformed the preamble transmission (e.g., if a dedicated preamble isused). For example, the additional information may include a WTRU groupidentity. For example, the additional information may include a WTRUstate (e.g., whether or not the screen is on, or similar). In anexample, the WTRU may receive a MSG2 message (e.g., RAR) that maycorrespond to a preamble transmitted with a second sequence in thepreamble format. The response may echo the second sequence, for example,for the RAR message using the Temporary C-RNTI field.

Although other physical layer configurations may be contemplated withinthe scope of numerous examples (e.g., a smaller number and/or largernumber of consecutive/non-consecutive physical resource blocks may beused for preamble transmission), a PRACH resource may include sixconsecutive resource blocks. In an example, a second set of PRACHresources may use a different number of PRBs. In LTE, the random accessformat may be designed to ensure good detection probability such that asufficient amount of energy may be collected at the receiver (e.g., asufficient number of PRBs allocated to preamble transmission), whileensuring that interference in the system may not be overly increased dueto timing misalignment (e.g., cyclic prefix, guard). The random accessformat may also be configured to ensure that false detection due toDoppler effects may be reduced or minimized (e.g., cyclic shift andsequence length).

Assuming that for a given set of PRACH resources, such characteristicsmay be less important than adding increased flexibility to the system,for example, while still allowing for the detection of a sufficientlylarge fraction of the preambles transmitted by WTRUs in a given coveragearea, then one possibility to reduce or minimize the overhead ofallocating additional PRACH resources may be to allocate fewer physicalresource blocks for the PRACH resources of a second set.

For example, allocating three PRBs may lead to 36 data subcarriers with15 kHz subcarrier spacing. The number of available subcarriers/data bitsin this case may be 432. 432 is not a prime number, and a prime numberof available subcarriers/data bits may increase or maximize the numberof available sequences. Considering a guard band similar as that of LTER10 preamble formats (e.g., using 25 subcarriers with spacing of 1.25kHz), in this case 23 subcarriers with spacing of 1.25 kHz may be used,and the number of available subcarriers/data bits may become 409. Theresulting possible random access preamble length in this case may beNzc=409. In an example, utilizing fewer PRBs may be based on adetermination that the PRBs that correspond to the second set of PRACHresources are mutually exclusive to the set of PRBs that corresponds toa first set of PRACH resources. In an example, utilizing fewer PRBs maybe based on a determination that the sets of PRACH resources utilizedset-specific RACH configurations, for example, if the sets utilized setspecific preamble transmission power settings.

A WTRU may be configured to handle RACH failure on a second set of PRACHresources. For example, a WTRU may reach a number of (e.g., the maximumnumber of) preamble transmissions for the second set of PRACH resources,for example, without determining that the procedure was successful. Inan example, the WTRU may determine that the RACH procedure isunsuccessful based on the WTRU reaching the maximum number of preambletransmission for the second set of PRACH resources without determiningthat the procedure was successful. The WTRU may simply stop preambletransmission without further actions (e.g., MAC may refrain fromnotifying RRC of the unsuccessful RACH procedure). In an example, if theWTRU determines that the RACH procedure was unsuccessful on the secondset of PRACH resources, the WTRU may declare UL RLF.

In an example, the WTRU may additionally perform one or more of thefollowing for a RACH procedure that is unsuccessful for preambletransmissions associated with a second set of PRACH resources. In anexample, upon a determination that a RACH procedure for a second set ofPRACH resources was unsuccessful, a WTRU may initiate a RA-SR on adifferent set of PRACH resources. For example, the WTRU may initiate aRA-SR of a first set of resources, for example, after a backoff time.The back off time may be used if no backoff indication (BI) and/or nocongestion indication is received. In an example, upon a determinationthat a RACH procedure for a second set of PRACH resources wasunsuccessful, a WTRU may initiate a RA-SR on a different set of PRACHresources (e.g., on a first set of resources) after a maximum number ofconsecutive unsuccessful attempts for a RACH procedure using the secondset of PRACH resources and/or after a maximum amount of time duringwhich a plurality of attempts have not succeeded. For example, thecounting and/or timer may be reset if any other successful dedicatedtransmission occurs and/or any other RACH procedure successfullycompletes for the WTRU. In an example, upon a determination that a RACHprocedure for a second set of PRACH resources was unsuccessful, a WTRUmay transmit the first preamble on the second set of resources using thepower level of the last attempt using a resource of the second set.

The WTRU may receive a configuration message that includes informationfor the WTRU to determine additional PRACH resources. As describedherein, in some examples, the configuration signaling may structure theadditional PRACH resources in corresponding sets of resources for agiven serving cell. The WTRU may receive such configuration in dedicatedsignaling (e.g., in a RRC Reconfiguration message with or without themobilityControlInformation IE) and/or on a BCCH in the broadcastedsystem information for the cell as part of the SI acquisition procedure.In an example, configuration of multiple sets of PRACH resources may bepermitted for a primary serving cell (PCell) and not in a secondarysevering cell (SCell). In an example, the WTRU configuration may beapplied to one or more secondary serving cells (SCell) for carrieraggregation, for example when a WTRU is in a RRC_CONNECTED state.

Combinations of the following are possible, where, for example, a firstset may correspond to a configuration received on a broadcast channel,and a second set may be received by dedicated signaling. In an example,the signaling described and/or the use of a second set of PRACHresources may be allowed after some form of activation. For example, theuse of a second set of PRACH resources may be allowed after entering asubstate of the RRC_CONNECTED state and/or upon some trigger (e.g., atrigger that activates procedures for dormancy).

The WTRU may use one or more of the following methods to configureadditional PRACH resources. For example, a WTRU may receive aconfiguration with multiple PRACH-Config IEs for a given serving cell(e.g., multiple PRACHs). For example, a WTRU may receive a configurationwith a second configuration for PRACH and/or with a correspondingconfiguration for RACH. Sending a second configuration may allow theextension part of an existing messaging to remain the same, and hencemay be relatively simple to introduce. Sending a second configurationmay create a completely separate PRACH channel, and the correspondingresources may be made to partly overlap with the first PRACH channel.For example, such a configuration (e.g.,rach-ConfigCommon-lowPrio-v12x0, and/or prach-Config-lowPrio-v12x0) maybe included as part of a non-critical extension in theRadioResourceConfigCommonSIB IE and/or as part of theRadioResourceConfigCommon IE, as shown as an example information element800 of FIG. 8 and an example information element 900 of FIG. 9,respectively.

For example, if one of the parameters of the second PRACH configuration(e.g., the PRACH-Config-lowPrio-v12x0 above) is not present, the WTRUmay use the corresponding parameter configured for the first PRACHconfiguration. In other words, if prach-ConfigIndex is not present,additional resources (e.g., possibly the second set of PRACH resources)may be realized by adding PRACH resources in the frequency domain usingprach-FreqOffset. If prach-FreqOffset is not present, additionalresources (e.g., possibly the second set of PRACH resources) may berealized by adding PRACH resources in the time domain usingprach-ConfigIndex.

For example, a WTRU may receive a configuration with an alternativemapping table for prach-ConfigIndex. For example, adding resources(e.g., possibly to realize a second set of PRACH resources) in the timedomain may be realized by redefining the meaning of the signaledconfiguration index (e.g., prach-ConfigIndex). This could be achieved,for example, by including an indication that the WTRU may use thealternative mapping table. Such an indication may be part of a dedicatedconfiguration. For example, the indication in theRadioResourceConfigCommon IE may be shown in an example informationelement 1000 of FIG. 10.

In an example, another method to add resources (e.g., possibly torealize a second set of PRACH resources) in the time domain may be toextend the range of the configuration index (e.g., prach-ConfigIndex).Additional bits may be introduced, for example, for a dedicatedconfiguration as described herein. In an example, the extended range maybe used to specify a first and a second set of resources on the PRACH ofthe given cell. FIGS. 11 and 12 illustrate example information elements1100 and 1200 that may be used to specify these sets of resources.

In an example, a WTRU may receive a configuration with multipleprach-ConfigIndex and/or multiple prach-FreqOffset for aPRACH-ConfigInfo. For example, the WTRU may receive a configuration witha second set of configuration parameters (e.g., prach-ConfigIndex) inthe time domain for the PRACH channel. For example, the WTRU may receivea configuration with a second set of configuration parameters (e.g.,prach-FreqOffset) in the frequency domain for the PRACH channel. Forexample, such a configuration may be realized by including an IE in thenon-critical extension in the RadioResourceConfigCommonSIB IE and/or inthe RadioResourceConfigCommon IE, as shown at an information element1300 of FIG. 13. The IE may supersede (as shown, except forrootSequenceIndex) and/or extend the signaled prach-Config IE, as shownat an information element 1400 of FIG. 14, appearing in that same IE.

Such a method may keep a single PRACH channel (e.g., including that asingle root index that may be used to generate the set of allocatedpreambles) in the serving cell while possibly extending the set ofavailable resources (e.g., possibly to realize a second set of PRACHresources). Such a signaling method may cause the configurationparameters of the PRACH channel to be separated into different IEs. Thesignaling may use the extension part of an existing message to indicatethat there are PRACH-related parameters in addition to those alreadysignaled in the fixed part of the message.

In an example, the WTRU may receive a configuration with additionalparameters for multiplexing in frequency and/or time domain. Forexample, the WTRU may receive a configuration with parameters thatdefine additional resources, for example structured as a second set ofPRACH resources. For example, such a configuration may be realized byincluding an IE in the non-critical extension in theRadioResourceConfigCommonSIB IE and/or in the RadioResourceConfigCommonIE, as shown at an example information element 1500 of FIG. 15. The IEmay supersede (as shown at an example information element 1600 of FIG.16, except for rootSequenceIndex) or extend the signaled prach-Config IEappearing in that same IE. Such a method may maintain a single PRACHchannel.

In an example, a WTRU may perform frequency multiplexing of PRACHresources in a PRACH occasion. For example, the PRACH configuration forframe structure 1 may be associated with a density value, for exampleper 10 ms. Any resource added in the frequency domain may be associatedwith a first or to a second set. The WTRU, given a density (e.g.,associated with the PRACH configuration index), may allocate resourcesin time first and then in frequency if the density cannot be met for thedensity value. In an example, the first resource block for the PRACH maybe based on signaled SFN period (e.g., SFN mod X=0), with a first PRB ina given subframe 0 and/or in given in frequency in that subframe, forexample as (PRB offset+6*(frequency resource index/2) if fra mod 2=0).

Such a scheme may be achieved by signaling “fra” for a given PRACHoccasion. The desired density may then be used by a WTRU to allocate oneextra PRACH opportunity in given PRACH occasion(s).

In an example, a WTRU may allow more than one PRACH version. PRACHversion may denote PRACH configurations with the same density but withdifferent subframe allocations. Different versions may enable processingload distribution in an eNodeB PRACH receiver serving multiple cells andnon-overlapping PRACH slots in neighboring cells. For example, in FDDdifferent versions may occupy different subframes, and in TDD severalversions may occupy the same subframes but different frequencies.

In an example, a WTRU may perform transmission of a preamble for apurpose other than to acquire resources for an uplink transmission. Forexample, the WTRU may determine that the preamble transmission isperformed for the purpose of proximity or range detection, to implementa keep-alive function, or a similar function. This may be useful, forexample, in a case in which a network node (e.g., an eNB) may implementa dormancy or a power saving state. In such a state, the eNB refrainfrom transmitting one or more signals in the downlink, perhapsrefraining from transmitting any signals in the downlink (e.g., whenthere is no WTRU to serve under the serving area of the eNB and/or ofthe cell). This may also be useful in a case in which a network node(e.g., an eNB) supports one or more cells in a frequency for which aWTRU does not perform measurements (e.g., in a high frequency band), butwhere the system may benefit from detecting proximity between a WTRU andthe eNB in question (e.g., millimeter wave (mmW) bands). For example,this may be useful in a system with multiple layers (e.g., with cellspossibly originating from different eNBs and/or in different frequencybands) where a cell or some cells (e.g., of a smaller coverage area) mayoverlap with one or more macro cells.

For example, the WTRU may initiate the transmission of a preamble on aspecific set of PRACH resources, for example using one or more of themethods disclosed herein. The transmission of the preamble may beinitiated from the reception of downlink control signaling from thenetwork. Such signaling may include a DCI received on the PDCCH and/orthe enhanced-PDCCH (E-PDCCH), which DCI may trigger a WTRU to performthe preamble transmission. For example, such signaling may include apaging message. In an example, the signaling may also include anindication that the request is for a specified function (e.g., a“keep-alive” or a proximity detection function) in which uplinkresources may not be granted as part of the procedure. The indicationmay be implicit or explicit. For example, an explicit indication mayinclude a field in the received control signaling that includes orindicates the indication. As another example, an implicit indication maybe determined from the combination of the parameters indicated for thepreamble transmission in the received control signaling and/or theconfiguration of the PRACH resources for the WTRU. For example, the WTRUmay determine that the indicated parameters correspond to a second setof PRACH resources in the configuration of the WTRU.

In this case, the WTRU refrain from autonomously performing aretransmission of the preamble. The WTRU may perform the retransmissionof a preamble if subsequent control signaling is received that triggersthe transmission of a preamble, for example, using the same set of PRACHresources, possibly with a different power level than for the previoustransmission. The WTRU may determine whether the preamble transmissionis an initial transmission or a retransmission if the control signalingis received within a certain time from the previous control signaling(e.g., within a signaling window).

If the WTRU determines that a preamble corresponds to a retransmission,the WTRU may apply power ramping, for example up to the maximum allowedpower for the concerned PRACH configuration. The power level or theamount of power ramping to apply to the transmission of the preamble maybe derived from an indication in the received control signaling. Thepower level may be configured with the corresponding PRACH configuration(e.g., it may be of a fixed value and it may correspond to the maximumallowed power for this PRACH configuration). For example, the WTRU mayreceive such configuration for the purpose of the “keep alive” orproximity detection function, with a power level that may correspond tothe maximum coverage of the cells in a given frequency layer.

If a preamble is transmitted according to any of the above methods, theWTRU may refrain from monitoring for a RAR using RA-RNTI.

The configuration of the set of PRACH resources for such functionalitymay correspond to resources of a first eNB, for example, of the (e.g.,macro) cell to which the WTRU is already connected, in which case it maybe assumed that a second network node (e.g., supporting a layer of asmall cell or small cells) that may implement a dormancy or a powersaving state may monitor the PRACH resource on the frequency of a cellof the first eNB. In an example, the PRACH resources may correspond toresources of a cell of the second network node (e.g., if the secondnetwork node monitors the concerned PRACH resources while in a dormantor power saving state).

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element can be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andcomputer-readable storage media. Examples of computer-readable storagemedia include, but are not limited to, a read only memory (ROM), arandom access memory (RAM), a register, cache memory, semiconductormemory devices, magnetic media such as internal hard disks and removabledisks, magneto-optical media, and optical media such as CD-ROM disks,and digital versatile disks (DVDs). A processor in association withsoftware may be used to implement a radio frequency transceiver for usein a WTRU, UE, terminal, base station, RNC, or any host computer.

What is claimed:
 1. A method for detecting cell congestion in a wirelesscommunication network, the method comprising: selecting, at a wirelesstransmit/receive unit (WTRU), a Physical Random Access Channel (PRACH)resource set out of a plurality of PRACH resource sets, wherein eachPRACH resource set of the plurality of PRACH resource sets comprises oneor more physical resource block (PRBs) that can be used for a preambletransmission, and each of the plurality of PRACH resource sets isassociated with a priority level; sending, from the WTRU, a preambletransmission to a cell during a random access procedure using one of theselected PRACH resource set; determining, at the WTRU, whether the WTRUreceived a Random Access Response (RAR); and determining, at the WTRU, acongestion state of the cell based on at least: the priority level ofthe selected PRACH resource set utilized for the preamble transmission,and at least one of whether the WTRU received a RAR or informationincluded in the RAR when the WTRU receives the RAR.
 2. The method ofclaim 1, wherein one or more of a random access channel (RACH) preambleused for the preamble transmission or a transmission opportunity usedfor the preamble transmission is selected based on a priority level ofdata to be transmitted to the cell during the random access procedure.3. The method of claim 1, further comprising: attempting to decode theRAR using a plurality of Random Access Radio Network TemporaryIdentifiers (RA-RNTIs), wherein decoding a transmission with a firstRA-RNTI of the plurality of RNTIs is an indication of networkcongestion; and determining that the cell is in the congested state ifthe RAR is successfully decoded using the first RA-RNTI.
 4. The methodof claim 1, further comprising: attempting to decode the RAR over aplurality of RAR windows; and determining that the cell is in thecongested state if the RAR is successfully decoded in a particular RARwindow of the plurality of RAR windows.
 5. The method of claim 1,further comprising: decoding the RAR to determine a value of a TemporaryCell Radio Network Temporary Identifier (C-RNTI) field, wherein apredetermined value of the C-RNTI field is used to indicate networkcongestion; and determining that the cell is in the congested state ifthe Temporary C-RNTI field comprises the predetermined value.
 6. Themethod of claim 1, wherein the WTRU fails to receive the RAR, and themethod further comprises determining that the network is in thecongested state based on the WTRU failing to receive the RAR and one ormore of a random access channel (RACH) preamble used for the preambletransmission or a transmission opportunity used for the preambletransmission.
 7. The method of claim 1, further comprising: attemptingto decode one or more physical downlink control channel (PDCCH)transmissions using a physical random access channel (PRACH) RadioNetwork Temporary Identifier (PR-RNTI), wherein transmissions that aresuccessfully decoded using the PR-RNTI comprise an indication ofresources to be used for subsequent random access procedures.
 8. Themethod of claim 1, further comprising, in response to determining thatthe cell is in the congested state, performing one or more of: abortinga Non-Access Stratum (NAS) Service Request; aborting an ongoing RadioResource Control (RRC) procedure; aborting an ongoing RRC connectionestablishment procedure; canceling transmission of data associated withan event that triggered the random access procedure; applying a backoffperiod before attempting a subsequent random access procedure;initiating a cell reselection procedure to select a different servingcell; performing a measurement to determine whether a failure to receivethe RAR is due to cell congestion or due to a poor radio link quality;initiating an alternative transmission method; or initiating a dormantbehavior.
 9. The method of claim 1, wherein sending the preambletransmission from the WTRU comprises indicating priority information inthe preamble transmission.
 10. The method of claim 9, wherein thepriority information is indicated using one or more of a preamble typeselection, a preamble selection, a random preamble selection, a preamblevalue selection, a preamble group selection, a Physical Random AccessChannel (PRACH) selection, a PRACH opportunity, a PRACH length, or apreamble length selection.
 11. The method of claim 1, furthercomprising: receiving a physical random access channel (PRACH)configuration, wherein the PRACH configuration comprises a PRACH RadioNetwork Temporary Identifier (PR-RNTI); and attempting to decode aPhysical Downlink Control Channel (PDCCH) using the PR-RNTI, whereingrants for higher priority random access procedures are successfullydecoded using the PR-RNTI.
 12. The method of claim 1, wherein the RARindicates a level of congestion.
 13. The method of claim 1, furthercomprising: receiving a PRACH configuration; and configuring theplurality of PRACH resource sets based at least in part on the receivedPRACH configuration.
 14. A wireless transmit/receive unit (WTRU)comprising: a transceiver; and a processor configured to: select, at theWTRU, a Physical Random Access Channel (PRACH) resource set out of aplurality of PRACH resource sets, wherein each PRACH resource set of theplurality of PRACH resource sets comprises one or more physical resourceblock (PRBs) that can be used for a preamble transmission, and each ofthe plurality of PRACH resource sets is associated with a prioritylevel; send, via the transceiver, a preamble transmission to a cellduring a random access procedure using one of the selected PRACHresource set; determine, at the WTRU, whether the WTRU received a RandomAccess Response (RAR); and determine, at the WTRU, a congestion state ofthe cell based on at least: the priority level of the selected PRACHresource set utilized for the preamble transmission, and at least one ofwhether the WTRU received a RAR or contents of the RAR when the WTRUreceives the RAR.
 15. The WTRU of claim 14, wherein the processor isfurther configured to determine the congestion state of the cell as afunction of the RAR.
 16. The WTRU of claim 14, wherein the processor isfurther configured to determine a preamble group to use for selection ofa Random Access Channel (RACH) preamble used for the preambletransmission based on a priority level of uplink data to be transmittedduring the random access procedure.
 17. The WTRU of claim 14, whereinthe processor is further configured to select from a subset of availablePhysical Random Access Channel (PRACH) resources for the preambletransmission.
 18. The WTRU of claim 17, wherein the subset of availablePRACH resources determined as a function of one or more of a systemframe number (SFN), a PRACH mask index, or a discontinuous reception(DRX) property.
 19. The WTRU of claim 14, wherein the processor isfurther configured to: decode the RAR; and determine that the cell is inthe congested state if the RAR includes an indication of congestion in apadding field of the RAR.
 20. The WTRU of claim 14, wherein the RARincludes a zero-size uplink grant and the processor is furtherconfigured to determine that the cell is in the congested state based onthe RAR including the zero-size uplink grant and a low priority beingindicated in the preamble transmission.
 21. The WTRU of claim 14,wherein sending the preamble transmission from the WTRU comprisesindicating priority information in the preamble transmission using oneor more of a preamble type selection, a preamble selection, a randompreamble selection, a preamble value selection, a preamble groupselection, a Physical Random Access Channel (PRACH) selection, a PRACHopportunity, a PRACH length, or a preamble length selection.
 22. TheWTRU of claim 14, wherein the processor is further configured to:receive a PRACH configuration; and configure the plurality of PRACHresource sets based at least in part on the received PRACHconfiguration.
 23. The WTRU of claim 14, wherein a first PRACH resourceset is utilized for low priority random access procedures and a secondPRACH resource is utilized for high priority random access procedures.24. The WTRU of claim 14, wherein the RAR indicates a level ofcongestion.